Management of Urinary Retention: Rapid Versus Gradual Decompression and Risk of Complications

Abstract

The literature was reviewed to quantify the risk of complications related to the relief of obstruction in urinary retention. We also sought to determine whether the risk of complications is higher with rapid or gradual decompression (or “clamping“) of the obstructed urinary bladder. The medical literature was identified by a search of the MEDLINE database and a manual review of the bibliographies of the identified articles. Studies show that, after quick, complete relief of obstruction, hematuria occurs in 2 to 16% of patients; however, clinically significant hematuria is rare. After relief of obstruction, blood pressure often decreases, but it usually normalizes and does not progress to clinically significant hypotension. Post-obstructive diuresis occurs after relief of obstruction in 0.5 to 52% of patients; however, it is easily managed and rarely of clinical significance. We were unable to identify any randomized controlled studies that directly compared quick, complete emptying with gradual emptying of the obstructed bladder. Moreover, we identified no studies supporting the practice of gradual emptying of the obstructed bladder. The available published studies support quick, complete emptying for relief of the obstructed urinary bladder. We conclude that hematuria, hypotension, and postobstructive diuresis may occur after decompression of the obstructed urinary bladder, but these complications are rarely clinically significant. Quick, complete emptying of the obstructed bladder is safe, simple, and effective and is recommended as the optimal method for decompressing the obstructed urinary bladder. Prudent, supportive care is needed for all patients, with special attention to elderly patients and those with hypovolemia. The literature was reviewed to quantify the risk of complications related to the relief of obstruction in urinary retention. We also sought to determine whether the risk of complications is higher with rapid or gradual decompression (or “clamping“) of the obstructed urinary bladder. The medical literature was identified by a search of the MEDLINE database and a manual review of the bibliographies of the identified articles. Studies show that, after quick, complete relief of obstruction, hematuria occurs in 2 to 16% of patients; however, clinically significant hematuria is rare. After relief of obstruction, blood pressure often decreases, but it usually normalizes and does not progress to clinically significant hypotension. Post-obstructive diuresis occurs after relief of obstruction in 0.5 to 52% of patients; however, it is easily managed and rarely of clinical significance. We were unable to identify any randomized controlled studies that directly compared quick, complete emptying with gradual emptying of the obstructed bladder. Moreover, we identified no studies supporting the practice of gradual emptying of the obstructed bladder. The available published studies support quick, complete emptying for relief of the obstructed urinary bladder. We conclude that hematuria, hypotension, and postobstructive diuresis may occur after decompression of the obstructed urinary bladder, but these complications are rarely clinically significant. Quick, complete emptying of the obstructed bladder is safe, simple, and effective and is recommended as the optimal method for decompressing the obstructed urinary bladder. Prudent, supportive care is needed for all patients, with special attention to elderly patients and those with hypovolemia. Urinary retention occurs commonly in men and women in both the ambulatory and the hospital settings; however, it is more frequent postoperatively and in men and elderly persons. The initial management of urinary retention includes drainage of urine from the distended bladder by catheter. Hematuria, hypotension, and postobstructive diuresis have occurred after bladder drainage by catheter, and the risk of these complications has been thought to be increased when the bladder is rapidly decompressed. As a result, the medical literature has recommended, and continues to recommend, gradual emptying as the method of choice in a patient with urinary retention.1Blandy J Emergency situations: acute retention of urine.Br JHospMed. 1978; 19: 109-111Google Scholar, 2Martinez-Maldonado M Kumjian DA Acute renal failure due to urinary tract obstruction.Med Clin North Am. 1990 Jul; 74: 919-932Google Scholar, 3Fontanarosa PB Roush WR Acute urinary retention.Emerg Med Clin North Am. 1988; 6: 419-437Google Scholar, 4Stine RJ Chudnofsky CR A Practical Approach to Emergency Medicine. 2nd ed. Little, Brown, Boston1994Google Scholar Nevertheless, some investigators continue to question the validity of this recommendation.5Bristoll SL Fadden T Fehring RJ Rohde L Smith PK Wohlitz BA The mythical danger of rapid urinary drainage.Am J Nurs. 1989; 89: 344-345Google Scholar, 6Upson C Kirby KA Catheter clamping after catheterization and rapid urine loss.Urol Nurs. 1995; 15: 63-64Google Scholar, 7Sueppel C Rapid or slow bladder decompression?.Urol Nurs. 1995; 15: 64-66Google Scholar Practicing clinicians seek answers to the following questions: What are the possible complications of urinary retention, how frequently do they occur, how should they be managed, and can decreasing the rate of urine release, by “clamping” a bladder catheter, prevent these complications? We searched the medical literature from January 1966 through December 1996 available through MEDLINE to address these issues. Multiple search strategies were used to identify all possible relevant articles. Examples of the subject headings and text words used include the following: urinary retention, urinary obstruction, continuous drainage, quick emptying, gradual release, fractionated drainage, clamping, hypotension, hematuria, and diuresis. All identified articles were reviewed to address the current controversies regarding the management of urinary retention and the associated complications. All relevant articles cited in the bibliographies of the retrieved articles were also reviewed. The information was synthesized and is presented herein in a discussion of the classification of urinary retention, complications of urinary retention (hematuria, hypotension, and postobstructive diuresis), and optimal rate of decompression. Acute urinary retention has been defined as that associated with suprapubic pain, whereas chronic urinary retention is painless.8O'Reilly PH Obstructive Uropathy. Springer-Verlag, New York1986Crossref Google Scholar In general, chronic urinary retention represents prolonged retention; however, the presence of pain is the criterion used to distinguish acute from chronic urinary retention. Chronic urinary retention has been further classified into two types, high-pressure chronic retention (HPCR) and low-pressure chronic retention (LPCR),9Abrams PH Dunn M George N Urodynamic findings in chronic retention of urine and their relevance to results of surgery.BMJ. 1978; 2: 1258-1260Crossref Scopus (93) Google Scholar based on the intrinsic detrusor pressure during the filling phase of micturition-high in HPCR and normal in LPCR. Incomplete voiding occurs with chronic urinary retention. As more urine fills the bladder, the pressure within the bladder remains within normal limits in LPCR. With HPCR, the bladder contains residual urine at higher than normal pressures, and as more urine fills the bladder, these pressures continue to increase. The presence of increased pressure is of critical importance because continuously increased bladder pressures in HPCR can lead to upper urinary tract damage. The manifestations of HPCR are unique: late-onset enuresis; a tense, palpable bladder; hypertension; and progressive renal impairment caused by the chronically increased urinary tract pressures.10George NJ O'Reilly PH Barnard RJ Blacklock NJ High pressure chronic retention.BMJ. 1983; 286: 1780-1783Crossref Scopus (84) Google Scholar Hypertension occurs in up to two-thirds of cases. Anatomically, HPCR is associated with bilateral hydronephrosis and bilateral hydroureters. The diagnosis of HPCR can be elusive because the initial manifestations may be hypertension, edema of the lower extremities, or renal failure.11Jones DA George NJ O'Reilly PH Barnard RJ Reversible hypertension associated with unrecognised high pressure chronic retention of urine.Lancet. 1987; 1: 1052-1054Abstract Scopus (32) Google Scholar, 12Ghose RR Birks JL Secondary hypertension accompanying high pressure chronic retention.Postgrad Med J. 1985; 61: 167-169Crossref Scopus (3) Google Scholar, 13Neal DE Irreversible renal failure in men with outflow obstruction: is it a preventable disease? [editorial].Postgrad Med J. 1990; 66: 996-999Crossref Scopus (6) Google Scholar In the series described by Jones and associates,11Jones DA George NJ O'Reilly PH Barnard RJ Reversible hypertension associated with unrecognised high pressure chronic retention of urine.Lancet. 1987; 1: 1052-1054Abstract Scopus (32) Google Scholar painless bladder distention and hydronephrosis were unsuspected in 24% of the 21 patients with HPCR. Therefore, HPCR should be considered in the assessment of an elderly patient with unexplained hypertension, edema of the lower extremities, or renal failure. After treatment, the long-term outlook for patients with HPCR is good.14Jones DA Gilpin SA Holden D Dixon JS O'Reilly PH George NJ Relationship between bladder morphology and long-term outcome of treatment in patients with high pressure chronic retention of urine.Br J Urol. 1991; 67: 280-285Crossref Scopus (24) Google Scholar LPCR represents retention at normal bladder pressures, before and after filling. Most patients with LPCR have outlet obstruction due to benign prostatic hypertrophy. They are able to produce high detrusor pressures for voiding and have the classic initial symptoms of hesitancy, decreased force of stream, and increased frequency. If symptoms are moderate to severe, obstruction can be relieved surgically or through pharmacologic methods; however, because bladder pressures are normal, urgent surgical intervention is unnecessary. The major complications of LPCR are acute urinary retention and infection. A separate, small subgroup of patients with LPCR can produce only low detrusor pressures. These patients have pronounced hesitancy and commonly use the Valsalva maneuver to maintain voiding. Unfortunately, surgical intervention is usually of little benefit in this subgroup of patients.8O'Reilly PH Obstructive Uropathy. Springer-Verlag, New York1986Crossref Google Scholar Hematuria.–Hematuria as a complication of the release of urinary tract obstruction has been a concern for many years. Quick, complete emptying of the bladder has been thought to be a predisposing factor for hematuria. In studies of quick, complete emptying, hematuria occurred in 2 to 16% of patients (Table 1). None of these studies, however, reported any episodes of severe hematuria, defined as hematuria significant enough to necessitate further invasive therapy (such as catheter irrigation or transfusions) or to cause death. In addition, none of the studies found an association between the initial bladder volume and the risk of hematuria.19Seifert E Die Blasenblutung ex vacuo.Zentralbl Chir. 1940; 67: 550-554Google ScholarTable 1Studies of Hematuria After Quick, Complete Emptying of Bladder*AUR = acute urinary retention; CI = confidence interval; NR = not reported.Reference†Glahn and Plucnar excluded known vesical tumors, prostate cancer, postoperative urologie procedures, and difficult catheterization; no exclusion criteria were described in the other studies. The study by Christensen and associates consisted of seven episodes of continuous and three of fractionated decompression.DesignTypeEpisodes (no.)Age (yr)HematuriaSevere hematuriaRangeMean%95% CI%95% CIGlahn & Plucnar,15Glahn BE Plucnar BJ Quick complete emptying of the bladder in 300 cases of urinary retention: the occurrence of haematuria.Dan Med Bull. 1984; 31: 68-70Google Scholar 1984ConsecutiveAUR3006–91621612.2, 20.500,1.2Christensen et al,16Christensen J Ostri P Frimodt-Moller C Juul C Intravesical pressure changes during bladder drainage in patients with acute urinary retention.Tirol Int. 1987; 42: 181-184Google Scholar 1987ConsecutiveAUR1066–8174.5100.3, 44.500, 30.5Paquinetal,17Paquin JM Perreault JP Faucher R Mauffette F Berlinguet JC Traitement de la phase aigue de la retention urinaire.J Urol (Paris). 1981; 87: 37-38Google Scholar 1981ConsecutiveAUR5031–90NR124.5, 24.300,5.8Brecher & Chwalla,18Brecher E Chwalla R Neues zur therapie der harnretention nebst Untersuchungen Uber die Entlastungsreaktion und die diurese bei chronischer harnstauung.Ztschr Urol Chir. 1931; 31: 266-312Google Scholar 1931RetrospectiveAUR300NRNRNRNR00,1.2Seifert,'9Abrams PH Dunn M George N Urodynamic findings in chronic retention of urine and their relevance to results of surgery.BMJ. 1978; 2: 1258-1260Crossref Scopus (93) Google Scholar 1940RetrospectiveAUR126NRNR20.5, 6.800,2.9* AUR = acute urinary retention; CI = confidence interval; NR = not reported.† Glahn and Plucnar excluded known vesical tumors, prostate cancer, postoperative urologie procedures, and difficult catheterization; no exclusion criteria were described in the other studies. The study by Christensen and associates consisted of seven episodes of continuous and three of fractionated decompression. Open table in a new tab Hypotension.–Hypotension and circulatory collapse after emptying of the obstructed bladder have been reported.20O'Connor VJ Observations on the blood pressure in cases of prostatic obstruction.Arch Surg. 1920; 1: 359-367Crossref Google Scholar The systemic blood pressure is increased by the urinary vesicovascular reflex in response to acute urinary distention and pain.21Lapides J Lovegrove RH Urinary vesicovascular reflex.J Urol. 1965; 94: 397-401Google Scholar, 22Taylor DE Viscero-vascular reflexes and the surgical patient.J R Coll Surg Edinb. 1966; 12: 61-67Google Scholar Taylor,22Taylor DE Viscero-vascular reflexes and the surgical patient.J R Coll Surg Edinb. 1966; 12: 61-67Google Scholar in studies of bladder emptying in animals and humans, showed that a sudden reduction in bladder wall tension reflexly produced vasodilatation with a concomitant decrease in blood pressure. Taylor concluded that a reduction in blood pressure occurs with no serious clinical consequences when a patient has healthy cardiovascular and nervous systems; however, a patient without the ability to compensate appropriately because of advanced age or hypovolemia may be at risk for prolonged hypotension after quick decompression of the bladder. Published studies that have commented or presented data on the occurrence of hypotension in association with quick, complete emptying of the bladder are summarized in Table 2. For our purposes, significant hypotension was defined as hypotension that was directly related to bladder decompression and that necessitated fluid resuscitation. These studies demonstrate a decrease in systemic blood pressure with quick, complete emptying; however, the actual change in blood pressure results in normalization of blood pressure without cardiovascular collapse.Table 2Studies of Blood Pressure Response With Relief of Urinary Retention*AUR = acute urinary retention; BP = blood pressure; DBP = diastolic blood pressure; HPCR = high-pressure chronic retention; NR = not reported; SBP = systolic blood pressure.Age (yr)Reference†Glahn and Plucnar excluded known vesical tumors, prostate cancer, postoperative urologie procedures, and difficult catheterization; no exclusion criteria were described in the other studies. The study by Christensen and associates consisted of seven episodes of continuous and three of fractionated decompression.DesignTypeEpisodes (N = 451)RangeMeanComments‡No studies documented significant hypotension.Glahn & Plucnar,15Glahn BE Plucnar BJ Quick complete emptying of the bladder in 300 cases of urinary retention: the occurrence of haematuria.Dan Med Bull. 1984; 31: 68-70Google Scholar 1984ConsecutiveAUR3006–9162“No cases of cardiovascular complications”Christensen et al,16Christensen J Ostri P Frimodt-Moller C Juul C Intravesical pressure changes during bladder drainage in patients with acute urinary retention.Tirol Int. 1987; 42: 181-184Google Scholar 1987ConsecutiveAUR1066–8174.5Significant median BP decrease, “none clinically important”George et al,10George NJ O'Reilly PH Barnard RJ Blacklock NJ High pressure chronic retention.BMJ. 1983; 286: 1780-1783Crossref Scopus (84) Google Scholar 1983ConsecutiveHPCR1425–8169BP normalized after emptyingGhose & Birks,12Ghose RR Birks JL Secondary hypertension accompanying high pressure chronic retention.Postgrad Med J. 1985; 61: 167-169Crossref Scopus (3) Google Scholar 1985CasesHPCR251–6357BP normalized after emptyingJones et al, 1987ConsecutiveHPCR1134–8771BP normalized after emptyingO'Connor,20O'Connor VJ Observations on the blood pressure in cases of prostatic obstruction.Arch Surg. 1920; 1: 359-367Crossref Google Scholar 1920NRNR5646–8661Mean decrease (mm Hg) in SBP = 40, DBP = 14; greatest decrease in SBP = 85, DBP = 45 (all but two in normal range after drainage)Taylor,22Taylor DE Viscero-vascular reflexes and the surgical patient.J R Coll Surg Edinb. 1966; 12: 61-67Google Scholar 1966NRAUR18NRNRNo significant complicationsLapides & Lovegrove,21Lapides J Lovegrove RH Urinary vesicovascular reflex.J Urol. 1965; 94: 397-401Google Scholar 1965NRAUR408–75NRExperimentally distended bladders, then released* AUR = acute urinary retention; BP = blood pressure; DBP = diastolic blood pressure; HPCR = high-pressure chronic retention; NR = not reported; SBP = systolic blood pressure.† Glahn and Plucnar excluded known vesical tumors, prostate cancer, postoperative urologie procedures, and difficult catheterization; no exclusion criteria were described in the other studies. The study by Christensen and associates consisted of seven episodes of continuous and three of fractionated decompression.‡ No studies documented significant hypotension. Open table in a new tab Postobstructive Diuresis.-In 1951, Wilson and colleagues23Wilson B Reisman DD Moyer CA Fluid balance in the urological patient: disturbances in the renal regulation of the excretion of water and sodium salts following decompression of the urinary bladder.J Urol. 1951; 66: 805-815Google Scholar first presented clinical evidence that renal impairment due to acute or chronic obstruction of the lower urinary tract can occasionally lead to such a copious loss of salt and water that life is endangered. More recent studies demonstrated that most cases of obstruction result in an increase in salt and water excretion, which is usually beneficial to the patient, by reversing a fluid overload state.11Jones DA George NJ O'Reilly PH Barnard RJ Reversible hypertension associated with unrecognised high pressure chronic retention of urine.Lancet. 1987; 1: 1052-1054Abstract Scopus (32) Google Scholar, 24Jones DA George NJ O'Reilly PH Barnard RJ The biphasic nature of renal functional recovery following relief of chronic obstructive uropathy.Br J Urol. 1988; 61: 192-197Crossref Scopus (24) Google Scholar, 25Jones DA George NJ O'Reilly PH Postobstructive renal function.Semin Urol. 1987; 5: 176-190Google Scholar Postobstructive diuresis has been arbitrarily defined as persistent urinary outputs that range from 125 to 200 mL/h.26Vaughan Jr, ED Gillenwater JY Diagnosis, characterization and management of post-obstructive diuresis.J Urol. 1973; 109: 286-292Google Scholar, 27Bishop MC Diuresis and renal functional recovery in chronic retention.Br J Urol. 1985; 57: 1-5Crossref Scopus (26) Google Scholar The true proportion of patients who experience postobstructive diuresis is unclear; however, the range is 0.5 to 52%, depending on how postobstructive diuresis is defined.26Vaughan Jr, ED Gillenwater JY Diagnosis, characterization and management of post-obstructive diuresis.J Urol. 1973; 109: 286-292Google Scholar27Bishop MC Diuresis and renal functional recovery in chronic retention.Br J Urol. 1985; 57: 1-5Crossref Scopus (26) Google Scholar Proposed mechanisms for this type of diuresis include osmotic diuresis due to urea,28O'Reilly PH Brooman PJ Farah NB Mason GC High pressure chronic retention: incidence, aetiology and sinister implications.Br J Urol. 1986; 58: 644-646Crossref Scopus (22) Google Scholar29Harris RH Yarger WE The pathogenesis of post-obstructive diuresis: the role of circulating natriuretic and diuretic factors, including urea.J Clin Invest. 1975; 56: 880-887Crossref Scopus (59) Google Scholar involvement of natriuretic and diuretic factors,22Taylor DE Viscero-vascular reflexes and the surgical patient.J R Coll Surg Edinb. 1966; 12: 61-67Google Scholar25Jones DA George NJ O'Reilly PH Postobstructive renal function.Semin Urol. 1987; 5: 176-190Google Scholar30Yarger WE Buerkert J Effect of urinary tract obstruction on renal tubular function.SeminNephrol. 1982; 2: 17-30Google Scholar disordered function of proximal or distal nephrons.30Yarger WE Buerkert J Effect of urinary tract obstruction on renal tubular function.SeminNephrol. 1982; 2: 17-30Google Scholar, 31Jones BF Nanra RS Post-obstructive diuresis.Aust N Z J Med. 1983; 13: 519-521Crossref Scopus (9) Google Scholar, 32Yarger WE Aynedjian HS Bank N A micropuncture study of postobstructive diuresis in the rat.J Clin Invest. 1972; 51: 625-637Crossref Scopus (66) Google Scholar, 33Jones DA Atherton JC O'Reilly PH Barnard RJ George NJ Assessment of the nephron segments involved in post-obstructive diuresis in man, using lithium clearance.Br JUrol. 1989; 64: 559-563Crossref Scopus (17) Google Scholar altered tubular permeability, 34Lorentz Jr, WB Lassiter WE Gottschalk CW Renal tubular permeability during increased intrarenal pressure.J Clin Invest. 1972; 51: 484-492Crossref Scopus (39) Google Scholar and disturbances in sodium-regulating hormones.35Clarke NW Jones DA Tames F Laing I George NJ Disturbance in sodium regulating hormones in chronic obstructive uropathy.Br J Urol. 1991; 68: 118-121Crossref Scopus (8) Google Scholar The actual cause is most likely a combination of these mechanisms. The clinical presentation does not predict which patients will have postobstructive diuresis. Significant diuresis has not been shown to correlate with the initial creatinine value or a subsequent decrease in the creatinine value.27Bishop MC Diuresis and renal functional recovery in chronic retention.Br J Urol. 1985; 57: 1-5Crossref Scopus (26) Google Scholar No correlation has been found between the severity or duration of postobstructive diuresis and the plasma urea value before decompression, electrolyte values, creatinine clearance, bladder pressure, or blood pressure.36Maher JF Schreiner GE Waters TJ Osmotic diuresis due to retained urea after release of obstructive uropathy.N Engl J Med. 1963; 268: 1099-1104Crossref Google Scholar Vaughan and Gillenwater26Vaughan Jr, ED Gillenwater JY Diagnosis, characterization and management of post-obstructive diuresis.J Urol. 1973; 109: 286-292Google Scholar studied 22 patients (age range, 34 to 85 years) who had postobstructive diuresis and found that patients with the greatest risk of significant postobstructive diuresis had fluid overload, severe renal impairment, or central nervous system manifestations. They also cautioned that excessive fluid replacement may prolong the diuresis by propagating it; they suggested replacement of two-thirds of the fluid output. Initial management of urinary tract obstruction, specifically the rate of release of the retained urine, has been debated for decades. The two primary methods to empty the obstructed bladder are rapid, complete emptying or gradual, slow emptying (or clamping of the urinary catheter). Proponents of gradual release advocate that gradual, slow emptying has a lower risk of associated complications, specifically hematuria and hypotension.37Bumpus Jr, HC Foulds GS Gradual emptying of over-distended bladder.JAMA. 1923; 81: 821-823Crossref Scopus (2) Google Scholar, 38Van Zwalenburg C Emptying a chronically distended bladder: description of a simple device.JAMA. 1920; 75: 1711Crossref Scopus (2) Google Scholar, 39Scott WW Gradual decompression of bladder with ureteral catheter.JUrol. 1928; 19: 81-88Google Scholar Various mechanisms have been suggested to explain the onset of hematuria after quick, complete emptying of the bladder, all based on sudden decompression causing injury to the urinary tract and resulting in hemorrhage. This theory, however, ignores the possibility of other etiologic factors contributing to the occurrence of hematuria, such as infection and iatrogenic trauma.40Creevy CD Sudden decompression of chronically distended urinary bladder: clinical and pathologic study.Arch Surg. 1932; 25: 356-385Crossref Google Scholar Alternatively, animal studies suggest that hematuria develops as a result of bladder wall damage that occurs before catheterization. Therefore, the rate of release is unrelated to the onset of hematuria.41Gould F Cheng CY Lapides J Comparison of rapid versus slow decompression of the distended urinary bladder.Invest Urol. 1976; 14: 156-158Google Scholar In addition, some investigators believe that gradual decompression blunts the vesicovascular reflex and avoids subsequent hypotension. Several methods have been suggested to accomplish gradual emptying of the bladder, including elevation of the tubing and collecting device, narrowing of the outlet diameter, and stepwise emptying of the bladder in small (200 to 300 mL) fractions.38Van Zwalenburg C Emptying a chronically distended bladder: description of a simple device.JAMA. 1920; 75: 1711Crossref Scopus (2) Google Scholar, 39Scott WW Gradual decompression of bladder with ureteral catheter.JUrol. 1928; 19: 81-88Google Scholar, 42Schonebeck J Kateterisering av urinblasa-ytterligare synpunkter.Lakartidningen. 1976; 73: 2192-2194Google Scholar These labor-intensive, time-consuming techniques are of unproven efficacy. No controlled studies have shown that gradual emptying of the obstructed bladder reduces the risk of complications. Furthermore, no estimates are available of the actual incidence of significant hematuria or other complications in association with gradual decompression of the obstructed bladder. Gradual release of the obstructed bladder continues to be recommended as the method of choice based on a theory that slow decompression of the intrabladder pressure will reduce the rate of complications.1Blandy J Emergency situations: acute retention of urine.Br JHospMed. 1978; 19: 109-111Google Scholar, 2Martinez-Maldonado M Kumjian DA Acute renal failure due to urinary tract obstruction.Med Clin North Am. 1990 Jul; 74: 919-932Google Scholar, 3Fontanarosa PB Roush WR Acute urinary retention.Emerg Med Clin North Am. 1988; 6: 419-437Google Scholar, 4Stine RJ Chudnofsky CR A Practical Approach to Emergency Medicine. 2nd ed. Little, Brown, Boston1994Google Scholar If a gradual reduction in intrabladder pressure is to be achieved, however, less than 50 mL of urine would need to be released. Two studies have quantified the decrease in intrabladder pressure as a function of released volume.16Christensen J Ostri P Frimodt-Moller C Juul C Intravesical pressure changes during bladder drainage in patients with acute urinary retention.Tirol Int. 1987; 42: 181-184Google Scholar43Osius TG Hinman Jr, F Dynamics of acute urinary retention: a monometric, radiographie and clinical study.J Urol. 1963; 90: 702-712Google Scholar These investigations have shown a decrease in intravesical pressure of approximately 50% with removal of the first 100 mL of urine. After this initial substantial decrease in pressure, the intravesical pressure declines only slightly. Christensen and associates16Christensen J Ostri P Frimodt-Moller C Juul C Intravesical pressure changes during bladder drainage in patients with acute urinary retention.Tirol Int. 1987; 42: 181-184Google Scholar compared quick, complete emptying with release of 100-mL fractions in patients with acute urinary tract obstruction. No significant complications were reported with either method. Results of fractionated release were similar to those of quick release-an initial, sudden decrease in intravesical pressure followed by minimal further reduction in pressures (Fig. 1). Therefore, to effect gradual reductions in intrabladder pressures, less than 50 mL of urine should be released from the bladder. A nursing survey showed that 57% of nurses practice gradual emptying; however, all release more than 750 mL initially before clamping the catheter.44Dodds P Hans AL Distended urinary bladder drainage practices among hospital nurses.Appl Nurs Res. 1990; 3: 68-72Abstract Full Text PDF Scopus (2) Google Scholar When performed in this manner, gradual emptying does not differ from quick, complete emptying. All available studies between 1920 and 1997 of the complications of relief of urinary retention are summarized in Table 1, Table 2. The available data analyzing relief of urinary retention are limited. A little more than 300 cases were studied within the past 20 years and none within the past 10 years. Most reported cases are of acute urinary retention relieved by quick, complete emptying, with only three of gradual decompression. The largest, most recent study by Glahn and Plucnar (1984)15Glahn BE Plucnar BJ Quick complete emptying of the bladder in 300 cases of urinary retention: the occurrence of haematuria.Dan Med Bull. 1984; 31: 68-70Google Scholar reviewed 300 episodes of acute urinary retention treated with quick, complete emptying. Consecutive hospital admissions, emergency department admissions, and inpatient episodes were analyzed. This treatment trial was limited, however, because it was not randomized or controlled. Of the 300 episodes that were observed, no significant complication was noted. No clinically significant complications were reported in any of the studies summarized in Table 1, Table 2. No randomized controlled trials have compared the outcomes of quick, complete emptying with those of gradual emptying of the obstructed urinary bladder. Such a study would be technically difficult to perform because of the need for repeated release of small fractions of urine (less than 50 mL, based on the results of the studies described) to effect gradual reduction of in the group adder intrabladder pressures in the group undergoing gradual emptying. In addition, significant hematuria and hypotension seem to be such infrequent complications that the study would need a large sample size to demonstrate statistically significant risk differences. Over time, populations and catheterization techniques have changed. As the general population ages, comorbid conditions become more prevalent, and patients are likely to have an increased risk of complications. Nonetheless, no published reports have noted increased complications due to bladder drainage. In LPCR, bladder pressures are normal at all times; therefore, complete emptying of the bladder is appropriate. In HPCR, bladder pressure is increased, but the same rationale for quick emptying in acute urinary retention applies.10George NJ O'Reilly PH Barnard RJ Blacklock NJ High pressure chronic retention.BMJ. 1983; 286: 1780-1783Crossref Scopus (84) Google Scholar The available literature supports the practice of quick, complete emptying of the obstructed urinary bladder. The literature lacks any evidence to support the practice of gradual emptying of the urinary bladder. Studies of bladder physiology suggest that gradual reduction of intrabladder pressures is difficult, if not clinically impossible, to accomplish. Additionally, as currently practiced, gradual emptying of the urinary bladder (or clamping) actually reduces intrabladder pressures rapidly. Of the cases reported in the literature, none were found in which death could be directly attributed to complications of quick, complete emptying of the bladder. On the basis of our review of the literature on management of urinary retention, we recommend quick, complete emptying of the obstructed urinary bladder in all instances. This method is easily performed and has not been shown in clinical trials to be associated with any increased risk of complications. No evidence supports the current practice of gradual emptying of the urinary bladder-specifically, clamping of the urinary catheter after release of 750 mL of urine. Hematuria and decreases in blood pressure occur with decompression of the bladder; however, these seem to be of little clinical consequence. Postobstructive diuresis occurs, perhaps frequently, but it is usually of benefit to the patient who generally is in a fluid-overload state. Management consists of judicious replacement of urinary output, with care not to perpetuate the diuresis with excessive fluid replacement. Prudent, supportive care for all patients is important; elderly patients and those with hypovolemia need special care.