Perirenal Stranding Research Articles

3D dynamic diuretic renal scintigraphy using a hybrid whole body CZT SPECT/CT camera protocol in the evaluation of acute ureteric obstruction caused by ureteric stone

PurposeTo investigate the performance of dynamic 3D diuretic renal scintigraphy using a hybrid whole body CZT SPECT/CT for the evaluation of acute ureteric obstruction in patients with urinary stone disease.Methods20 patients who presented to the Emergency Department with acute renal colic due to urinary stone disease confirmed by means of CT were prospectively included. Three observers evaluated and graded hydronephrosis, hydroureter, perirenal stranding, and thickening of the renal fascia from the CT as well as the renal scintigraphy curves from the dynamic SPECT study. The normalized residual activity from dynamic SPECT was analysed at 16 min in all patients and at 20 min in suspected obstruction.ResultsRenal scintigraphy curves showed a sensitivity of 100%, specificity of 93%, PPV 83% and a NPV 100% for obstruction, while normalized residual activity showed a sensitivity of 100%, specificity of 73%, PPV 56% and a NPV 100%. All patients presented at least 2 secondary signs of obstruction on the CT, showing a PPV of only 25% for obstruction.ConclusionDynamic 3D diuretic renal scintigraphy CZT SPECT/CT provides valuable functional and anatomical information from one single examination. The combination of pathological renogram curves and high normalized residual activity values provide the most valuable imaging information to determine the presence of acute ureteric obstruction. The secondary signs of obstruction observed on CT are not specific and should not be used to confirm or discard obstruction in patients with urinary stone disease.Trial registration: ISRCTN15338358. Registration date 03/01/2024. Retrospectively registered. https://www.isrctn.com/ISRCTN15338358?q=miguel%20ochoa%20figueroa&filters=&sort=&offset=1&totalResults=2&page=1&pageSize=10

Prediction of spontaneous distal ureteral stone passage using artificial intelligence.

Identifying factors predicting the spontaneous passage of distal ureteral stones and evaluating the effectiveness of artificial intelligence in prediction. The files of patients presenting with distal ureteral stones were retrospectively evaluated. Those who experienced spontaneous passage were assigned to Group P, while those who did not were assigned to Group N. Demographic and clinical data of both groups were compared. Then, logistic regression analysis was performed to determine the factors predicting spontaneous stone passage. Based on these factors, a logistic regression model was prepared, and artificial intelligence algorithms trained on the dataset were compared with this model to evaluate the effectiveness of artificial intelligence in predicting spontaneous stone passage. When comparing stone characteristics and NCCT findings, it was found that the stone size was significantly smaller in Group P (4.9 ± 1.7mm vs. 6.8 ± 1.4mm), while the ureteral diameter was significantly higher in Group P (3.3 ± 0.9mm vs. 3.1 ± 1.1mm) (p < 0.05). Parameters such as stone HU, stone radiopacity, renal pelvis AP diameter, and perirenal stranding were similar between the groups. In multivariate analysis, stone size and alpha-blocker usage were significant factors in predicting spontaneous stone passage. The ROC analysis for the logistic regression model constructed from the significant variables revealed an area under the curve (AUC) of 0.835, with sensitivity of 80.1% and specificity of 68.4%. AI algorithms predicted the spontaneous stone passage up to 92% sensitivity and up to 86% specifity. AI algorithms are high-powered alternatives that can be used in the prediction of spontaneous distal ureteral stone passage.

Does the kidney actually swell during an acute urinary tract obstruction?

The appearance of renal swelling during an acute obstruction of the urinary tract could be caused by hydronephrosis or an increase of the parenchymal volume. To the best of our knowledge no studies have been performed regarding renal parenchymal volume change during an acute urinary tract obstruction. To investigate the change in renal parenchymal volume during an acute urinary tract obstruction and to correlate any such volume change to the degree of secondary signs of obstruction. In total, 20 patients with obstructive ureterolithiasis were retrospectively and randomly included. Two observers measured the parenchymal volume of the obstructed and the contralateral kidney in CT examinations before, during, and after obstruction. Hydronephrosis, hydroureter, perirenal stranding, and thickening of the renal fascia were graded and correlated to volume change. A decreased volume was noted after obstruction in the obstructed kidneys (-24%) (P < 0.0001) and in the contralateral kidneys (-5%) (P = 0.0110) with a positive correlation of change in volume (P = 0.011). The volume of the obstructed kidneys was larger than the contralateral kidneys during obstruction (P < 0.0001) but not after obstruction (P = 0.559). No significant difference in volume was found before compared to after obstruction. Secondary signs of obstruction did not correlate to volume change. The parenchymal volume increases in the obstructed kidneys as well as in the contralateral kidneys during obstruction. The increase in volume was larger in the obstructed kidneys compared to the contralateral kidneys. After obstruction the kidneys regained their original volume. Secondary signs did not correlate to volume change.

Is conservative management safe in patients with acute ureterolithiasis and perirenal stranding?

In patients presenting with ureterolithiasis, perirenal stranding is frequently observed in non-contrast computed tomography. Because perirenal stranding may be caused by tears in the collecting system, previous studies have described an increased risk of infectious complications and suggested broad empiric antibiotic therapy and immediate decompressing of the upper urinary tract. We hypothesized that these patients can also be managed conservatively. Therefore, we retrospectively identified patients with ureterolithiasis and perirenal stranding and compared diagnostic and treatment characteristics as well as treatment outcomes between patients undergoing conservative versus interventional management by ureteral stenting, percutaneous drainage or primary ureteroscopic stone removal. We classified perirenal stranding as mild, moderate or severe based on its radiological extent. Of 211 patients, 98 were managed conservatively. Patients in the interventional group had larger ureteral stones, more proximal ureteral stone location, more severe perirenal stranding, higher systemic and urinary infectious parameters, higher creatinine levels, and received more frequent antibiotic therapy. The conservatively managed group experienced a spontaneous stone passage rate of 77%, while 23% required delayed intervention. In the interventional and conservative groups, 4% and 2% of patients, respectively, developed sepsis. None of the patients in either group developed a perirenal abscess. Comparison of perirenal stranding grade between mild, moderate and severe in the conservatively treated group showed no difference in the spontaneous stone passage and infectious complications. In conclusion, conservative management without prophylactic antibiotics for ureterolithiasis and perirenal stranding is a valid treatment option as long as no clinical or laboratory signs of renal failure or infections are observed.

A radiologist’s approach to CT KUB for the urologist

In this article we review the computed tomography imaging features of renal and ureteric calculi, the secondary signs of renal tract calculi and their possible complications. Most calculi appear as high-density foci due to their composition, whereas other signs that may be appreciated include the soft-tissue rim sign in the ureter, upstream renal tract dilation and peri-ureteric or peri-renal stranding. The most accurate means of measuring a calculus is in the coronal plane on bone windows. We also provide a systematic approach to interrogating computed tomography of the kidneys, ureter and bladder for the urologist, with examples of other conditions that may present as renal colic and are apparent on computed tomography. Level of evidence: Not applicable as no original research is being proffered.

Predictive value of secondary signs of obstruction in follow-up computed tomography of ureteral stones: a study with dynamic computed tomography

Objectives: This study aimed to determine the ratio of obstruction and predictive values of secondary signs in follow-up computed tomography (CT) of ureterolithiasis patients; to correlate stone characteristics with obstruction; to compare enhancement of obstructed and non-obstructed kidneys; and to compare radiation dose of the dynamic CT protocol to an excretory-phase protocol.Materials and methods: This retrospective study assessed 49 follow-up CT scans of patients with remaining ureterolithiasis after a renal colic episode. Obstruction was measured as time taken to excretion of contrast medium in dynamic CT. Degree of secondary signs of obstruction was evaluated from the unenhanced CT. Data were collected on patients’ gender and age, stone size and location, time from renal colic to follow-up, attenuation of the renal cortex and radiation dose.Results: Obstruction was present in 28% (n = 14) at follow-up. Predictive values (sensitivity, specificity, positive predictive value, negative predictive value) were calculated for hydronephrosis (1.0, 0.63, 0.52, 1.0), hydroureter (1.0, 0.4, 0.4, 1.0), perirenal stranding (0.21, 0.94, 0.6, 0.75), Gerota’s fascia (0.21, 0.97, 0.75, 0.76) and renal swelling (0.21, 0.97, 0.75, 0.76). Obstruction was not correlated with stone characteristics. Enhancement was lower in obstructed kidneys (p < 0.01). Radiation dose was reduced by 43% (1.8 mSv).Conclusions: Obstruction was found in 28% of patients. Secondary signs were scarce and of indeterminate value to the diagnosis of obstruction. The absence of hydronephrosis and hydroureter contradicted obstruction. Stone characteristics were not correlated with obstruction. Enhancement of the renal cortex was lower in obstructed kidneys. The dynamic protocol reduced the radiation dose.

Renal and perirenal space involvement in acute pancreatitis: An MRI study

ObjectivesTo study the prevalence and characteristics of renal and perirenal space involvement and its relation to the severity of acute pancreatitis (AP) using MRI. Methods115 patients with AP who underwent MRI with the clinical kidney function test were retrospectively analyzed in this study. MRI sequences included conventional and diffusion weighted imaging (DWI) sequences. The renal and perirenal space involvement in AP was noted on MRI. The renal apparent diffusion coefficient (ADC) on DWI was measured for each kidney. The severity of AP on MRI was graded using MR severity index (MRSI). The relationships among the renal and perirenal space involvement on MRI, the renal ADC, MRSI and the results of the kidney function test were analyzed. ResultsIn the 115 patients with AP, the renal and perirenal space abnormalities detected included renal parenchymal abnormalities (0.8%), abnormalities of the renal collecting system (2.6%), renal vascular abnormalities (1.7%), thickened renal fascia (99%), perirenal stranding (62%) and perirenal fluid collection (40%). The prevalence of perirenal space abnormalities was correlated with the severity of AP based on MRSI (P<0.05). The renal ADC values were lower in patients with abnormal kidney function than in those without kidney injury (P<0.05). The prevalence of kidney function abnormalities was 9.4%, 32% and 100% in mild, moderate, and severe AP cases, respectively (P=0.00). ConclusionPerirenal space involvement is much more than renal parenchymal involvement in AP. The prevalence of perirenal space involvement in AP on MRI has a positive correlation with the severity of AP according to MRSI.

Comparison of secondary signs as shown by unenhanced helical computed tomography in patients with uric acid or calcium ureteral stones

Unenhanced helical computed tomography (UHCT) has evolved into a well-accepted diagnostic method in patients with suspected ureterolithiasis. UHCT not only shows stones within the lumen of the ureter, it also permits evaluation of the secondary signs associated with ureteral obstruction from stones. However, there we could find no data on how secondary signs might differ in relation to different compositions of ureteral stones. In this study, we compared the degree of secondary signs revealed by UHCT in uric acid stone formers and in patients forming calcium stones. We enrolled 117 patients with ureteral stones who underwent UHCT examination and Fourier transform infra-red analysis of stone samples. Clinical data were collected as follows: age, sex, estimated glomerular filtration rate (eGFR), urine pH, and radiological data on secondary signs apparent on UHCT. The uric acid stone formers had significantly lower urine pH and eGFR in comparison to calcium stone formers, and on UHCT they also had a higher percentage of the secondary signs, including rim sign (78.9% vs. 60.2%), hydroureter (94.7% vs. 89.8%), perirenal stranding (84.2% vs. 59.2%) and kidney density difference (73.7% vs. 50.0%). The radiological difference was statistically significant for perirenal stranding (p=0.041). In conclusion, we found that UHCT scanning reveals secondary signs to be more frequent in patients with uric acid ureteral stones than in patients with calcium stones, a tendency that might result from an acidic urine environment.

Native spiral computerized tomography in patients with acute flank pain--sense or nonsense?

To compare the diagnostic efficacy and costs of native spiral-CT and intravenous urography (IVU) in the management of patients with acute flank pain. Native spiral-CT and IVU (following about 30 minutes after CT) were compared in 66 patients with acute flank pain followed by an IVU. The spiral-CT protocol was: 5-mm section thickness, 7.5-mm table feed and 3-mm increment. The analysis conducted independently by two radiologists entailed: (a) Morphology: presence of stone disease (yes-no), localization and size of calculi, periureteral and perirenal stranding, dilatation of the collecting system, and possible alternative diagnoses and (b) cost-effectiveness: direct and indirect costs. Fifty-two patients had urolithiasis. The detection rate of renal and ureteric calculi was significantly higher with native spiral-CT than with IVU (100% vs. 69%, respectively) (p < 0.05). A specific sign of ureteric calculi was the so-called soft tissue "rim sign" (sensitivity 82% and specificity 100%, respectively). In 13 of 14 patients with acute flank pain with no evidence of urolithiasis alternative diagnoses could be made by spiral-CT. Spiral-CT was significantly more cost-effective than IVU in management. Native spiral-CT is faster, more effective and less expensive than IVU in the management of patients with acute flank pain. Additionally, it poses less risk and has the capability for allowing alternative diagnoses. Therefore, unenhanced spiral-CT should be the first line modality in patients with acute flank pain.

Acute ureteric calculus obstruction: unenhanced spiral CT versus HASTE MR urography and abdominal radiograph

The aim of this study is to compare the performance of unenhanced spiral CT to the combination of HASTE MR urography (MRU) and plain abdominal radiography (KUB) in patients suspected of having acute calculus ureteric obstruction. 64 patients with suspected acute calculus ureteric obstruction were evaluated. The presence of perirenal fluid, presence and level of ureteric obstruction and calculi were assessed on both techniques. 44 of 64 (69%) patients had acute calculus ureteric obstruction based on clinical, radiographic or surgical findings. MRU showed perirenal fluid in acute ureteric obstruction (77%) with a greater sensitivity than CT showed stranding (45%). The combination of fluid and ureteric dilation on MRU showed a sensitivity of 93% (CT 80%), specificity of 95% (CT 85%), and accuracy of 94% (CT 81%). There were 61 findings of either fluid or ureteric dilatation on MRU in 44 acutely obstructed kidneys compared with 37 similar findings on CT (p<0.005). Although there was excellent reproducibility (Kappa=/>0.75) in the finding of perirenal fluid on MRU, there was only fair interobserver agreement (Kappa<0.4) regarding perirenal stranding on CT. MRU/KUB showed ureteric calculi in 21/29 (72%) of patients with calculi seen by CT. Overall, MRU/KUB revealed 2.4 abnormalities per acutely obstructed ureter compared with 1.8 abnormalities detected by CT. MRU/KUB using HASTE sequences can diagnose the presence of acute calculus ureteric obstruction with similar accuracy to spiral CT. The technique has less observer variability and is more accurate than CT in detecting evidence of obstruction such as perirenal fluid.

Perirenal MR high signal — A new and sensitive indicator of acute ureteric obstruction

This study was carried out to determine the incidence of perirenal magnetic resonance (MR) high signal in acute ureteric obstruction as demonstrated by half-Fourier acquisition single shot turbo spin-echo (HASTE) MR. In addition, we evaluated the sensitivity of this perirenal MR high signal as a predictor of acute ureteric obstruction. A prospective evaluation of 55 consecutive patients with suspected ureteric obstruction was carried out using the HASTE MR sequence. Images were compared to concurrent IV urography (IVU) or to computed tomography (CT) where these were available. Acute and chronic ureteric obstruction were differentiated by clinical evaluation. Forty-one patients had obstructed kidneys. HASTE MR accurately predicted the presence of acute ureteric obstruction in 20/23 (87%) based on presence of perirenal MR high signal. None of these showed evidence of contrast medium extravasation on the concurrent i.v. urogram. 15/18 (83%) chronically obstructed kidneys demonstrated no perirenal high signal on HASTE MR, and the remaining three showed only a trace of perirenal high signal. CT showed perirenal stranding in only 2/8 patients with acutely obstructed kidneys. In acute ureteric obstruction, HASTE MR shows perirenal high signal intensity much more commonly than IVU shows extravasation or CT showing perirenal stranding. The origin of this MR signal is uncertain but may represent oedema, lymphatic distension or free fluid from forniceal rupture. HASTE MR can accurately distinguish between acute and chronic ureteric obstruction based on the degree of perirenal high signal.