Hemodialysis and iopamidol clearance after subclavian venography.

RATIONALE AND OBJECTIVES: The dialyzability of iopamidol is unknown and was investigated in patients undergoing long-term hemodialysis for chronic renal failure. METHODS: Ten patients received 30 ml Niopam 300 (Bracco SpA, Milan, Italy) (identical to 18372 mg iopamidol) intravenously into a forearm vein to investigate for occult subclavian stenosis. RESULTS: The elimination half-life of iopamidol before hemodialysis was 69.6 hours and during 4 hours of hemodialysis was 3.5 hours. A single 4-hour hemodialysis cleared 55.7% (95% Ci 51-5-59.8) of the administered dose, while second and third dialyses cleared 25.3% (95% Ci 21.4-29.1) and 10.1% (95% Ci 7.7-12.6) of the administered dose, respectively. Two patients with significant residual urine excretion excreted more than 10% of the administered dose in the urine. For anuric patients, extrarenal clearance provided total body clearance of up to 0.266 L/hr. CONCLUSIONS: Hemodialysis is a rapid and efficient means of clearing iopamidol provided it is performed soon after the contrast study.

Clearance of iopamidol, a non-ionic contrast medium, by CAPD in patients with end-stage renal failure.

In normal healthy subjects radiographic contrast media are cleared by the kidneys with a half-life of approximately 2 h and a total body clearance of 8 l/h. The mechanism of contrast clearance has not been previously investigated in chronic renal failure patients undergoing continuous ambulatory peritoneal dialysis (CAPD). A study was undertaken to investigate the pharmacokinetics of a non-ionic water soluble radiographic contrast medium (iopamidol) in 10 patients stabilized on CAPD. All patients (eight male, two female) aged 22-68 years (median 53 years) had injection of 30 ml of iopamidol 300 via a forearm vein to investigate subclavian vein patency following previous cannulation for haemodialysis. Venous blood samples, CAPD dialysate and urine were collected for seven days post injection. The mean plasma half-life was 37.9 h (SD 10.6) (range 24.1-57.2 h) for the CAPD patients and was greatly prolonged in comparison to healthy subjects. The total body clearance of iopamidol was also greatly reduced (0.377 l/h). CAPD removed an average of 53.6% of the administered dose (range 36.3-80.8%) whilst an average of 26.9% was excreted in the urine (range 1.3-56.3%). The combined renal and dialysate clearance was up to 93% of the administered dose over the period of the study. There is therefore some evidence for a small extra renal clearance of iopamidol in end-stage renal failure patients. This study has shown for the first time that patients with end-stage renal failure undergoing CAPD have significantly delayed elimination of contrast medium. This should be taken into consideration when extensive or prolonged investigations using contrast medium are proposed.

Polyarthropathy--a delayed reaction to low osmolality angiographic contrast medium in patients with end stage renal disease.

Since the introduction of low osmolality non-ionic media, acute reactions to radiographic contrast are uncommon and delayed reactions are especially rare, consisting mostly of mild flu-like symptoms. We report two patients suffering from end-stage renal failure and treated by continuous ambulatory peritoneal dialysis (CAPD) who developed a severe constitutional illness including acute polyarthropathy 6 and 16 h after injection of the low osmolality non-ionic contrast medium, iopamidol. Although the clinical presentation of the reactions was similar to a systemic lupus syndrome there was no immunological evidence to support this as an aetiological mechanism. Since CAPD is a relatively inefficient method of clearing contrast media prolonged high circulating levels of iopamidol may have been a contributory factor to these unusually severe delayed contrast reactions.

Technetium labelled red blood cell scintigraphy in the diagnosis of intestinal haemorrhage.

99m-Technetium labelled red blood cell scintigraphy was used in the investigation of 15 adult patients with suspected small or large bowel bleeding requiring at least five units of blood (mean 14.3 units) and one neonate with rectal bleeding. Scintigraphy was found to be an accurate method of detecting the site of haemorrhage and was superior to angiography. This technique may be of particular value in patients with profuse colonic haemorrhage when the view at colonoscopy is poor.

Percutaneous nephrostomies.

A review was made of 127 percutaneous nephrostomies (PCN) in 106 patients with benign (74 patients) and malignant (32 patients) urinary tract obstruction. Data on underlying aetiology, complications, subsequent management and long-term management are presented. The study confirms that PCN is an effective and safe method of providing temporary or prolonged urinary diversion in obstruction. Its use in pelvic malignancy should be determined by the likelihood of obtaining worthwhile prolonged palliation in individual patients.

Phlebography in the salage of dialysis fistulae.

Provision of long-term satisfactory vascular access for haemodialysis is an increasing problem. The functional life of an arteriovenous fistula can be greatly extended by an active salvage policy to which radiology makes an invaluable contribution. Forty-seven consecutive patients with vascular access problems were studied, 11 undergoing forearm phlebography and 36 phlebography of a malfunctioning fistula. Of the 11 patients with forearm phlebograms, only one patient had a fistula constructed that was not used for dialysis, despite demonstration of a patent forearm venous system; and in three patients operation was avoided after demonstration of inadequate veins. Only three of the 36 fistulograms failed to give useful information, whereas in seven patients operation was avoided by demonstration of a normal fistulogram.

The additional value of intraoperative angiography in infragenicular reconstruction.

OBJECTIVE: To evaluate the ability of preoperative intraarterial digital subtraction angiography (IADSA) to predict the feasibility of infragenicular reconstruction and site of the distal anastomosis. DESIGN: Prospective study. SETTING: University Hospital MATERIALS: 45 patients with 50 ischaemic limbs, considered potential candidates for infragenicular reconstruction. CHIEF OUTCOME MEASURES: Pre-reconstruction intraoperative angiography (IOA) was used as the gold standard. Analysis of angiograms was performed blindly and independently by a single observer. In patients who ultimately underwent primary amputation, exploration and attempted angiography of the crural and ankle vessels was performed to verify the IADSA findings. MAIN RESULTS: There was 87% accuracy (kappa = 0.66) between IADSA and IOA in differentiating between a normal, stenosed and occluded tibial artery and there was 86% accuracy (kappa = 0.67) in determining the adequacy of run-off into the pedal arch. IADSA had a positive predictive value of 100% to determine the feasibility of reconstruction but a negative predictive value of only 73%. After excluding those patients tha IADSA deemed non-reconstructable, IADSA had a positive predictive value of 97% to determine the correct artery and 92% to determine the correct segment of artery for distal anastomosis. CONCLUSIONS: IADSA could not determine when reconstruction was not possible, but in those deemed reconstructable by IADSA, the surgeon can confidently expose the appropriate artery at the appropriate level knowing the pedal run-off status in 86% of patients. IADSA should not be used to exclude reconstruction (i.e. pre-reconstruction IOA is still required in these patients) but for the remainder, IADSA can be used to plan surgical strategy without recourse to IOA.

Prospective study of routine scrotal ultrasonography in urological practice.

The value of routine scrotal ultrasonography has been evaluated in a prospective study of 109 men with scrotal symptoms or signs. Ultrasonography had a sensitivity of 100% and specificity of 99% for testicular tumour. Clinically useful information was provided in 53% of patients and 8% might have avoided surgery if the ultrasound report had been heeded. Ultrasonography did not provide any additional information in patients with scrotal pain and an entirely normal scrotum clinically, and in those with epididymal cysts in whom the testis was palpably normal. If these 2 groups had been excluded from routine scrotal ultrasonography there would have been a 25% reduction in the number of examinations without any reduction in diagnostic yield.

Localization of lower gastrointestinal bleeding using in vivo technetium-99m-labelled red blood cell scintigraphy.

Technetium-99m-labelled red blood cell scintigraphy was used in the investigation of 41 patients with major rectal haemorrhage. Red cells were labelled in vivo with technetium-99m pertechnetate and serial scans (0-36 h) were taken using a large field gamma camera. Twenty-two men and 15 women, mean age 71.3 years (range 32-91 years), and four children were studied. Forty-three scans were performed in all and there were 31 positive and 12 negative results. In each case the accuracy of the scan in localizing the bleeding site was checked either by independent investigations or at laparotomy. A definite bleeding site was identified in 30 cases and red cell scintigraphy correctly localized 29 of these (sensitivity 97 per cent). In the remaining 13 cases a bleeding site was not identified by any of the independent investigations and in this group there were two false positive scans (specificity 85 per cent). The investigation had a high predictive value when both positive (94 per cent) and negative (92 per cent). These data suggest that technetium-99m-labelled red cell scintigraphy should be used more widely in the investigation of patients with suspected lower gastrointestinal haemorrhage.

A prospective study of the value of conventional CT, dynamic CT, ultrasonography and arteriography for staging renal carcinoma.

The value of dynamic CT scanning for staging renal carcinoma was studied prospectively in 28 patients and the results compared with those of ultrasonography, arteriography and conventional CT. Arteriography correctly staged 48% of tumours; ultrasonography and conventional CT correctly staged 50% and dynamic CT correctly staged 72%. Dynamic CT staged renal carcinoma more accurately than ultrasonography, conventional CT or arteriography and it is suggested that arteriography should be restricted to specific indications such as the mapping of arterial anatomy and therapeutic renal artery embolisation.