mL Of Iohexol Research Articles

Attenuation values of the intracranial arterial and venous vessels by bolus injection of various contrast agents: a study with a single-detector helical CT scanner

We evaluated the arteriovenous contrast on the source images of intracranial three-dimensional computed tomography (CT) angiography (3D-CTA) using a high-concentration (370 mg I/ml) contrast agent in comparison with intermediate-concentration (300 mg I/ml) contrast. With a fixed intravenous injection rate and scanning delay, 3D-CTA was performed using a single-detector helical CT scanner in 30 consecutive patients. We used 100 ml of iohexol 300 for 10 patients, 100 ml of iopamidol 300 for 10 patients, and 80 ml of iopamidol 370 for 10 patients. Attenuation values of the bilateral internal carotid arteries, bilateral middle cerebral arteries, basilar artery trunk, bilateral cavernous sinuses, bilateral basal veins, and Galenic vein were measured quantitatively on the axial CT angiographic source images. High-concentration contrast significantly increased the attenuation values of the intracranial arterial system without increasing the attenuation of the venous system. High-concentration contrast is helpful for obtaining valuable arteriovenous contrast on source images with intracranial 3D-CTA.

Case 107: Lymphoma of the Mesentery

A 59-year-old man with a history of hepatitis C infection underwent abdominal computed tomography (CT) for surveillance of possible progression of hepatitis C and to rule out hepatocellular carcinoma. He had no clinical history of fever, abdominal pain, or palpable masses. There was no history of prior surgery or radiation therapy, and he was seronegative for human immunodeficiency virus. Physical examination findings were normal, and all laboratory tests were negative. Abdominal CT was performed with 800 mL of 2% diatrizoate meglumine and sodium (Gastrografin; Bracco Diagnostics, Princeton, NJ) administered orally and 140 mL of iohexol (300 mg of iodine per milliliter) (Omnipaque; Nycomed, New York, NY) administered intravenously. A triple-phase liver protocol was used. Images were obtained in the portal venous and late arterial phases. The delayed phase images are not shown.

Utility of 16-MDCT Angiography for Comprehensive Preoperative Vascular Evaluation of Laparoscopic Renal Donors

Our objective was to determine the efficacy of 16-MDCT angiography in preoperative evaluation of vascular anatomy of laparoscopic renal donors. Fifty-five consecutive renal donors (25 men and 30 women) underwent 16-MDCT angiography followed by donor nephrectomy. In the arterial and nephrographic phases, images were acquired with 60% overlap and 0.6-mm reconstruction in both phases after 120 mL of iohexol was injected at 4 mL/sec. On a 3D workstation, images were evaluated retrospectively by two abdominal imagers blinded to surgical results with respect to number and branching pattern of renal arteries and major and minor renal veins. These CT angiography results were compared with surgical findings. The surgically confirmed sensitivity of both reviewers (1 and 2) using the MDCT data for detection of renal arteries was 98.5% (65 of 66), and accuracies were 97.0% for reviewer 1 and 95.5% for reviewer 2. Sensitivity and accuracy detection of renal veins was 97% (61 of 63) and 98% (62 of 63) for reviewer 1 and reviewer 2, respectively. Sensitivity and accuracy detection of early arterial bifurcation (< 2 cm from aorta) was 100% (14 of 14), and sensitivity in detection of late venous confluence (< 1.5 cm from aorta) was 100% (8 of 8). All major renal venous variants were identified; reviewer 1 identified 78% (18 of 23) minor venous variants, and reviewer 2 identified 83% (19 of 23) minor venous variants. There were no hemorrhagic complications at surgery. Excellent agreement between reviewers (kappa = 0.92-0.97) was achieved for detection of normal and variant anatomy. 16-MDCT angiography enabled excellent preoperative detection of arterial anatomy and venous laparoscopic donor nephrectomy.

(735): Epidural steroid injection efficacy is a function of the contrast dispersion pattern

Epidural steroid injections (ESI) may provide relief of radicular pain associated with lumbar disc herniations. Inflammation from a disc herniation occurs primarily in the ventral epidural space at the site of the disc injury. Epidural steroids should therefore, be deposited at the level of the disc lesion in the ventral epidural space. Epidural needle placement can be accomplished by one of three methods: caudal (C), translaminar (TL) or transforaminal (TF). The purpose of this study is to analyze epidurogram contrast dispersion patterns in the epidural space using the three routes of epidural needle placement. After patient informed consent and IRB approval, 60 patients with L5-S1 disc herniations were randomly assigned to have epidural steroid injections by one of three methods for epidural needle placement; caudal (n=20), translaminar (n=20) and transforaminal (n=20). Each procedure was performed with fluoroscopy using a 22 gauge Tuohoy needle. Each patient received 3 ml of iohexol 300 with 5 ml preservative saline with 40 mg of triamincolone in Groups TL and TF and 20 ml preservative saline with 40 mg steroid in Group C after proper needle placement was ascertained by epidurogram observation. Fluoroscopy was repeated at 30 min post injection. Statistical analysis was done using the Fisher Exact test with p <0.05 to reject the null hypothesis. Observed epidural contrast dispersion patterns were; V=ventral, AP =anterior-posterior and P= posterior; Caudal (n=20), V=0/20 (0%), AP=11/20(55%), P=9/20, (45%); Translaminar (n=20) V=2/20 (10%), AP= 8/20 (40%), P=10/20 (50%) and Transforaminal (n=20), V=18/20 (90%), AP, 2/20 (10%), P=0/20 (20%). Pain relief two weeks following the ESI was as follows: C, 9/20 (45%), TL, 10/20 (50%), TF, 15/20 (75%). Transforaminal ESI resulted in significantly (p<0.05) greater pain relief with a single epidural steroid injection which is attributed to a higher incidence of steroid placement within the ventral epidural space.

Simulation of Aortic Peak Enhancement on MDCT Using a Contrast Material Flow Phantom: Feasibility Study

The objective of our study was to develop a flow phantom simulating aortic peak enhancement after the injection of contrast material on CT and to investigate the validity of the flow phantom by comparing the time-enhancement curves obtained for the flow phantom and humans. We developed a flow phantom simulating the enhancement pattern of the aorta after the injection of contrast material. In protocols 1, 2, and 3 of the phantom study, 90, 102, and 150 mL of iohexol, respectively, was administered over 35 sec. In protocol 4, 102 mL of iohexol was administered over 25 sec. In phantom protocols 1', 2', and 3', the dose and contrast injection duration were the same as in protocols 1, 2, and 3; however, saline (10 mL) was injected during the 20 sec after contrast delivery. In the human study, 20 patients were randomized into four groups: Groups A, B, and C received 1.5, 1.7, and 2.5 mL of iohexol per kilogram of body weight, respectively, over 35 sec; and group D received 1.7 mL/kg over 25 sec. In patient groups A, B, C, and D, phantom protocols 1, 2, 3, and 4 were used, respectively. Single-level serial CT scans were obtained using a 16-MDCT scanner on the simulated and real aortas after the injection of contrast material. Time-enhancement curves of simulated and real aortas were generated, and aortic peak times and aortic peak enhancement values were calculated. Aortic peak enhancement and aortic peak times in protocols 1-4 and 1'-3' of the phantom study were 2-8% larger and 6-18% longer, respectively, than in the corresponding patient study. The shape of the time-enhancement curves before aortic peak time in protocols 1-3 and 1'-3' of the phantom study closely resembled that of the corresponding patient study. After the aortic peak time, the shape of time-enhancement curves in protocols 1, 2, and 3 of the phantom study was different from the corresponding patient study; however, it was similar in phantom protocols 1'-3' and the corresponding patient study. In all four phantom protocols, the difference between maximal and minimal aortic peak enhancement was less than the SD of the corresponding patient study. The level of peak aortic enhancement and the time to peak aortic enhancement were similar in the phantom and human studies when we used our different contrast injection protocols for MDCT.

Safety of Contrast Venography prior to Caval Interruption in Patients with Renal Insufficiency

We undertook this study to determine whether the use of contrast venography would adversely affect renal function in patients with renal insufficiency requiring caval interruption. We conducted a retrospective review of all inferior vena cava (IVC) filters inserted at our institution over a 2-year period (January 2002 to January 2004). The indication for caval interruption, insertion technique, type of filter used, pre- and postintervention creatinine level, and the presence of diabetes and hypertension were analyzed. A total of 282 IVC filters were inserted, with 38 of them placed in patients with renal insufficiency as defined by a serum creatinine level of > 1.5 mg/dL. Contrast venography with 15 to 30 mL of iohexol (Omnipaque 300) was used in all cases, and no special measures other than proper hydration were used for renal protection. All filters were successfully deployed. The mean +/- SD preintervention creatinine level was 2.38 +/- 0.79 mg/dL. The mean +/- SD postintervention creatinine levels at 2 and 30 days were 2.26 +/- 0.45 mg/dL and 2.12 +/- 0.94 mg/dL, respectively. No patients required hemodialysis following caval interruption, and no adverse effect on renal function was noted. Contrast venography accurately delineates venous anatomy and facilitates proper caval filter placement with no apparent adverse effect on renal function. We believe contrast venography is safe even in the presence of renal insufficiency.

Transendocardial Delivery of Extracellular Myocardial Markers by Using Combination X-ray/MR Fluoroscopic Guidance: Feasibility Study in Dogs

To demonstrate the feasibility of using a combination of x-ray fluoroscopic and magnetic resonance (MR) fluoroscopic (ie, x-ray/MR fluoroscopy) guidance for left ventricular (LV) catheterization and transendocardial delivery of extracellular tissue markers. Experiments were performed in six dogs by using an x-ray/MR fluoroscopy system. The arterial guide wire and catheter were advanced into the heart with x-ray fluoroscopic guidance. The dogs were injected with 0.5, 1.0, and 2.0 mL of iohexol. For passive catheter tracking, a steady-state free precession MR imaging sequence was used. A steerable dual-lumen catheter was used to transendocardially inject a mixture of gadodiamide (0.05 mol/L) plus Evans blue dye (3%). An electrocardiographically gated dual-inversion-recovery MR imaging sequence was used to visualize the myocardial delivery of the gadodiamide-blue dye mixture. A high concentration of gadodiamide (0.5 mol/L) was used to demarcate the borders of the area of interest, or "hit the target." Blood pressure, heart rate, and oxygen saturation were measured before and after the intervention. Analysis of variance, Scheffé, and paired Student t tests were used for data analysis. LV catheterization via arterial access was feasible with two-dimensional x-ray fluoroscopic and three-dimensional MR fluoroscopic guidance. Delivery of the gadodiamide-blue dye mixture and the consequences of the procedure were monitored with MR imaging. Gadolinium-enhanced regions were bright on T1-weighted MR images, but they varied in size as a function of injectant volume. The mean sizes of these regions were 1.5% +/- 0.6 of the LV after the 0.5-mL injection of the mixture and 7.0% +/- 0.5 of the LV after the 2.0-mL injection (P <.001, Scheffé test). The corresponding mean sizes of the blue dye-enhanced regions were 2.3% +/- 0.6 and 8.3% +/- 0.4, respectively (P <.001). A high concentration of gadodiamide caused signal intensity loss around the gadolinium-enhanced regions. Transendocardial delivery of potential therapeutic solutions is feasible with x-ray/MR fluoroscopic guidance. The injection catheter can be navigated with MR imaging guidance to hit the target.

Electrical nerve stimulation using a stimulating catheter: what is the lower limit?

Objectives To minimize the risk of intraneural injection when performing nerve blocks, some authors caution against injecting through a needle placed with motor responses observed at nerve stimulator output settings of 0.3 mA or less. We present a case of placing a continuous cervical paravertebral catheter with brisk motor response while stimulating the catheter at 0.05 mA, with no adverse sequelae. Case report A 56-year-old man scheduled for rotator cuff repair received a continuous cervical paravertebral block for intraoperative and postoperative pain control. A stimulating catheter was used for the block. During catheter placement, nerve stimulator output was decreased to 0.05 mA at 300 μs and the motor response remained brisk. The patient was not significantly sedated and experienced no pain during placement or with injection of 40 mL of 0.5% ropivacaine through the catheter. Narcotic drugs were not required during surgery, and the block provided excellent postoperative pain control. Catheter position was evaluated by fluoroscopy to further identify the catheter’s relationship to the brachial plexus. The nerve trunks of C5 and C6 were clearly visible after 1 mL of iohexol (Omnipaque) was injected through the catheter. The catheter was removed the following day. At the follow-up visit 2 weeks later, the patient’s neurological examination remained unremarkable. Conclusion We present a single case of successful placement of a stimulating catheter with no neurological injury even when motor response occurred at very low nerve stimulator output settings.

Optimization of contrast agent volume for helical CT in the diagnostic assessment of patients with severe and multiple injuries.

The aim of this study was to determine the optimal amount of contrast agent for helical CT of the trunk during primary radiologic evaluation of polytraumatized patients. Eighty-three patients with severe and multiple injuries (mean age 36.2 years) underwent standardized helical CT examination with administration of a single contrast agent bolus of iohexol (Accupaque 300) at volumes of 120, 150, and 180 ml. Image quality was estimated by two blinded radiologists using a visual analogue scale. Analysis further included density measurements in regions of interest (ROIs) placed in the ascending, descending, and abdominal aorta as well as in the liver and spleen. The qualitative rating of the contrast agent effect after administration of 150 and 180 ml was significantly better compared with 120 ml [odds ratio (OR) 12.05, 95% confidence interval (CI) 3.50-41.52 and OR 12.14, 95% CI 3.36-43.85, respectively]. A dose increase from 120 to 150 ml resulted in a significantly better enhancement of the abdominal aorta (p = 0.006). The highest dose of 180 ml was not associated with a diagnostic gain in the other ROIs. We recommend administration of 150 ml of iohexol as the optimal amount of contrast material for single phase bolus administration in emergency helical CT examination of the chest and abdomen.

Assessment of aortic invasion by pulmonary carcinoma with the use of intra-aortic endovascular sonography: A case report

J Thorac Cardiovasc Surg 2001;122:1041-2

Plasma Iohexol Clearance in Automated Peritoneal Dialysis -its Role in Adequacy Determination

To compare the relationship of plasma iohexol clearance to standard adequacy measures in an automated peritoneal dialysis (APD) population. Prospective, nonrandomized, open label, simultaneous clearance studies of novel (iohexol) and traditional (urea and creatinine) markers of dialysis quantitation. Outpatient peritoneal dialysis units associated with tertiary care university hospitals. Eighteen stable patients, 13 undergoing continuous cycling peritoneal dialysis (CCPD) and 5 receiving intermittent dialysis, who underwent 24-hour clearance studies were enrolled in and completed the study. Each subject received 15 mL of iohexol intravenously the morning of a scheduled dialysis night. Blood was obtained for determination of serum concentrations of urea nitrogen and creatinine, and plasma iohexol concentration. Dialysate and urine were collected over 24 hours. Urea and creatinine data from the total pooled dialysate and from the 24-hour urine collection were used to calculate daily Kt/Vurea and normalized total daily creatinine clearance (CrCl). Total plasma iohexol clearance was calculated using a one-compartment model with the Brochner-Mortensen correction. Normalized [to 1.73 m2 body surface area (BSA)] iohexol clearance correlated very well with normalized CrCl (r2 = 0.777; p < 0.001). A weaker correlation was observed between Kt/Vurea and normalized iohexol clearance (r2 = 0.213; 0.05 < p < 0.1). When data are not normalized using BSA or urea distribution volume, the regressions are improved for both creatinine (r2 = 0.820) and urea (r2 = 0.533). These results were comparable between those on CCPD and those on intermittent therapy. Total plasma iohexol clearance provides a simple assessment for APD adequacy by eliminating collection problems inherent to the methodologies currently employed. Such simplicity allows for more frequent assessments of delivered dialysis dose and efficacy of prescription changes.

Liver perfusion studied with ultrafast CT.

Our goal was to quantify absolute hepatic arterial and portal venous perfusion noninvasively in patients with and without liver disease using ultrafast CT. A single slice through the porta hepatis was repeatedly scanned after bolus injection of 25 ml of iohexol 300 mg I/ml, followed by a 25 ml saline "chaser" intravenously at 10 ml/s. Thirty-nine controls, 7 cirrhotic patients, and 5 patients with known metastases on the slice plane were studied; hepatic arterial perfusion was determined in 41 patients and portal venous perfusion in 24. Time-attenuation curves from regions of interest drawn over the liver, spleen, aorta, and portal vein were analysed. Hepatic arterial perfusion was calculated by dividing the peak gradient of the liver time-attenuation curve prior to the time of peak splenic attenuation by the peak aortic CT number increase. Splenic perfusion was calculated by dividing the peak gradient of the splenic time-attenuation curve by the peak aortic CT number increase. Portal perfusion was derived by scaling the splenic time-attenuation curve by the ratio of hepatic arterial/splenic perfusion. This scaled curve was subtracted from the liver time-attenuation curve to give a portal curve. The peak up-slope of this curve was divided by the peak rise in splenic or portal vein density. Hepatic arterial perfusion averaged 0.19 ml/min/ml (n = 31) in controls and was raised in cirrhosis to 0.25 ml/min/ml (n = 6) and metastases 0.43 ml/min/ml (n = 4). Portal venous perfusion was 0.93 ml/min/ml (n = 19) in controls and 0.43 ml/min/ml (n = 4) in cirrhosis. Reproducibility has been confirmed. Dynamic ultrafast CT shows potential in quantifying arterial and portal hepatic perfusion. The technique may be adaptable to dynamic bolus MRI.

The effect of radiographic contrast media on leukocyte motility.

Studies describing the effects of radiographic contrast media (RCM) in leukocyte chemotaxis have been contradictory. No studies have been performed after in-vivo exposure. The authors assess the effect of RCM on leukocytes following in-vivo exposure. Seventeen patients were studied after intraarterial bolus injection of 75 mL of iohexol (300 mg/mL) or iotrolan (300 mg/mL), 30 minutes and 24 hours postinjection; chemotaxis was assessed using an ex-vivo whole-blood under-agarose method. With iohexol, there was a profound reduction in chemotaxis compared with the preinjection state (P = .001) at 30 minutes. No effect, however, was seen at 24 hours. With iotrolan, no significant reduction in chemotaxis was seen at 30 minutes or at 24 hours. Radiographic contrast media have differing effects on leukocyte chemotaxis. This may be of significance in the selection of appropriate RCM in certain patients.

Contrast Bolus Dynamic Computed Tomography for the Measurement of Solid Organ Perfusion

The authors have investigated the aortic responses to various intravenous bolus injections of nonionic and ionic contrast media and have presented data illustrating the potential of ultrafast computed tomography (CT) to quantify perfusion in the kidney, liver, and spleen. Bolus Dynamics Study: Performed in 3 healthy dogs (weight: 35 kg to 36 kg). In 2 dogs, 15 mL of the nonionic agent iohexol and the ionic agent sodium-meglumine diatrizoate were injected at 5, 10 and 20 mL/sec via a venous catheter placed in the superior vena cava; the order of injection was alternated between the 2 dogs. In the third dog, 25 mL of iohexol 300 mg I/mL was compared with diatrizoate 370 mg I/mL with injection rates of 10 and 20 mL/sec. Computed tomography scanning at the level of the midabdominal aorta was performed using an ultrafast CT scanner. Time-density curves were drawn for regions of interest over the aorta, and gamma-variate fits performed. Perfusion Studies: Dynamic perfusion scans of the upper abdomen were performed in more than 50 patients. A dose of 25 mL of iohexol 300 mg I/mL was injected at 10 mL/sec via an intravenous cannula in the antecubital fossa, followed immediately by 25 mL of saline, at the same rate. Scanning was performed at a single level using an ultrafast CT scanner. Regions of interest were drawn and gamma-variate fits were applied to the vascular time-density curves. Bolus Dynamics: Excellent curve fits for aortic time-density curves were obtained. A 10-mL/sec versus a 5-mL/sec bolus produced an 8% higher peak density. Nonionic contrast increased the peak density by a mean of 6%, increased the area under the corrected time-density curve by a mean of 22%, and lengthened the increase time by a mean of 21%. Perfusion Studies: Values obtained were reproducible and correlated well with values predicted from inert gas washout techniques. Changes in the CT number in a region after an intravenous injection of contrast medium may be used to calculate blood flow per unit volume of tissue. Ultrafast CT offers sufficient data points for accurate calculation. The quality of the aortic bolus is of great importance. Nonionic media offer several important advantages: hemodynamic perturbation is minimized, and they are better tolerated at the high injection rates needed. Low-osmolality nonionic agents produce "better" curves than conventional high-osmolality ionic agents, all other factors being equal. The resulting data are relevant to intravenous digital subtraction angiography and indirect portography as well as to perfusion measurement. The technique of quantitative dynamic CT is theoretically applicable to any cross-sectional modality, notably magnetic resonance.

Low-osmolality contrast media: Dosage comparison of ioversol and iohexol for cranial computed tomography

One hundred patients undergoing cranial computed tomography were evaluated in this prospective, randomized, double-blind comparative study. Patients received 50 mL of ioversol 320 (16 g iodine), 75 mL of ioversol 320 (24 g iodine), 100 mL of iohexol 240 (24 g iodine), 100 mL of iohexol 300 (30 g iodine) or 150 mL of iohexol 240 (36 g iodine). Twenty patients were enrolled in each treatment group. No patient in any treatment group experienced any contrast-media-related adverse reaction. Results of this study coupled with our prior work suggests that the lowest dose and optimal concentration of low-osmolality contrast media necessary to produce diagnostic cranial computed tomography is 32 g of iodine administered in a concentration of 320 mg/100 mL iodine.

A Simple Technique for Cervical Myelography

A new method has been devised for obtaining high-quality cervical myelograms safely and easily through lumbar injection. This method uses simple radiographic equipment, and does not require a tiltable table or fluoroscopy. Fifty-seven patients with cervical disorders were examined by this method using 9.5 ml of iohexol (300 mg l/ml), and successful myelograms were obtained in all patients. No serious complications were encountered.

Effects of Contrast Media on Myocardial Function During Acute Left Ventricular Failure in the Dog

We studied the hemodynamic side effects of intracoronary injection of contrast media during acute ischemic heart failure by using anesthetized dogs. Induction of failure was performed by microembolization of the area supplied by the left main coronary artery. Six ml of iohexol (Omnipaque) increased contractility during the normal state, while this contrast medium induced no alterations in any of the recorded hemodynamic variables during left ventricular failure. Ioxaglate (Hexabrix) was also well tolerated during the normal state, while sodium-meglumine diatrizoate (Renografin) markedly decreased systolic variables. However, in the failing heart both ioxaglate and diatrizoate resulted in greater reduction in all systolic variables than in the normal heart. We conclude that both ionic contrast media may be harmful in acute ischemic heart failure. Non-ionic iohexol appears safer in this condition.

The effect of intrathecal iohexol on visual evoked response latency: A comparison including incidence of headache with iopamidol and metrizamide in myeloradiculography

Fifty consecutive unselected patients referred for myeloradiculography and examined by the same radiologist, when facilities for measuring the visual evoked response were available, are considered. The effect on the visual evoked response of the examination and the incidence of headache following the use of iohexol as the contrast medium are compared with those after the use of iopamidol and metrizamide reported in a previous study. A total of 400 cases examined with iopamidol and 200 cases examined with iohexol are reviewed with regard to the incidence of headache. Whereas iopamidol and, to a greater extent metrizamide, were found to cause significant lengthening of the visual evoked response latency 20 hours after the radiological examination, iohexol did not. Furthermore there was no significant difference in the 20 hour reading following the use of iohexol compared with the original control group of patients who underwent lumbar puncture alone. There was a lower incidence and severity of headache following the use of iohexol than with iopamidol and a markedly reduced incidence compared with metrizamide. Iohexol is considered less neurotoxic than iopamidol which had previously superceded metrizamide as the contrast medium used for myeloradiculography in the Royal Surrey County Hospital. Volumes of up to 14 ml of iohexol 300 mg I/ml have been used for lumbar radiculography and for total myelography and up to 10 ml for direct lateral cervical puncture. In 350 cases examined to date with iohexol the only serious sequel was a case of chemical meningitis following the lumbar injection of 10 ml of the 300 mg I/ml solution for a cervical examination. The patient made an uneventful recovery.

Rectal biopsy in patients presenting to an infectious disease unit with diarrhoeal disease.

The role of sigmoidoscopy and rectal biopsy was investigated in patients referred to an infectious diseases unit with diarrhoea. Seventy-four patients were studied. Nine patients (12%) had inflammatory bowel disease, either ulcerative colitis or Crohn's disease. Thirty-six patients (48%) had infective diarrhoea. A wide variety of conditions accounted for the diarrhoea in the remaining patients. Sigmoidoscopy was abnormal in 25 patients and rectal biopsy in 56. The abnormalities in rectal mucosal histology were classified into six grades. Some patients with infective diarrhoea showed rather characteristic histological changes which may be of diagnostic value. Eight showed features which suggested a diagnosis of inflammatory bowel disease. However, repeat rectal biopsy in the convalescent period showed a striking improvement in the patients with infective diarrhoea. In contrast, the histological changes persisted in the patients with inflammatory bowel disease. Repeat rectal biopsy may be essential before making a firm diagnosis of inflammatory bowel disease in some patients who present with diarrhoea and apparently typical histological changes.