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BPRRR #001 – Ureter October 17, 2007

Posted by tomography in BPRRR, Nuclear Medicine.
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Here are the summaries of some of the articles I have read this week. These deal with the issue of peristalsis of the ureter, which is a hot topic among urologists and surgeons. Feel free to comment on these, or to offer further reading. You may also write your own BPRRR article and have it published here!

1: Br J Urol. 1993 Feb;71(2):156-60. ” Non-invasive investigation of normal individual ureteric activity in man.”

Ureter peristalsis in not easy to study. For instance, x-ray contrast materials can increase diuresis, thus alter the results, while the Whitaker test is a typically invasive technique. Therefore data obtained by these methods may not be realistic. Fast-frame renography was first described by Müller and Schauenberg in 1985, and this method, though refined, has been used to safely study ureter peristalsis.

The authors of this paper conducted (2,5 sec/frame) fast-frame renography on 5 males, who underwent a 12 hour fasting the night before the experiment. Before the scan they were asked to void so as to facilitate urine production, and they were asked again after the scan. Following the first scan, all subjects were re-hydrated with water at the rate of 5ml/kg/h for 6 hours and another scan was taken.

3 ureters showed an increase, 1 showed no change, and 5 showed a decrease in peristalsis. 1 ureter achieved tubular flow, in which the ureter acts as a hollow tube. Interestingly, their results found no significant change between the dehydrated and the hydrated states. They also concluded that ureters of the same person may react to increased urine production differently, and that the speed of the boluses do not change regardless of hydration.

2: Br J Urol. 1993 Feb;71(2):130-6. ” Validation of a non-invasive radioisotope method of imaging ureteric urine transport.”

I have mentioned before that ureter peristalsis may be detected in several ways, for example direct observation, x-ray technique, and MRI radiography. But dynamic renal scintigraphy or renography has the least amount of side-effects, and it is the least demanding on the patient. In order for a technique to gain use in the everyday clinical practice is has to be validated to previously accepted methods.

This article describes how renography has been validated in the porcine model. The animals were not given water 12h before the experiment so that they became oliguric. They were sedated with ketamine and they were given desmopressin to stop intrinsic urine production. Midline laparotomy was performed so that the left kidney and ureter were accessible. A catheter was positioned transparenchymaly so that its tip lay in the pelvis of the kidney, and bodywarm infusion containing 99-Th-DTPA was administered into the kidney. A pair of EMG (electromyography) electrodes were placed on the ureter to detect ureteral contraction. Cystotomy was also performed and the left ureteric orifice catheterized. Urine drops ascending through this catheter were detected by a photoelectric drop counter. The animal was positioned in front of a gamma camera, so that scintigraphy (2,5 sec/frame fast-frame renography) could be performed.

The researchers concluded that a bolus of urine passing down the ureter represented by a spindle on the compressed image (scintigram) corresponds to readings by the EMG and the drop counter, therefore renography is a valid technique to study ureter peristalsis.

3: Br J Urol. 1989 Feb;63(2):144-8.”Radionuclide Imaging of Ureteric Peristalsis.”

A couple things to know about ureteral peristalsis: the frequency is set by pacemaker cells, that lie in the pelvis of the kidney. The physiological range is between zero and four / min. The speed of a bolus of urine ascending the ureter remains constant (15-20 mm/s) regardless of hydration.

These authors obtain renograms from 3 patients. The first one is a 65-year-old male with no history of urological problems. In his case, a peristalsis between 2-3/min is recorded after hydration, which is in correlation with the expected results. The second patient is a 44-year-old female with a lower ureteric obstruction. A frequency of 5/min. is recorded above the obstruction and no peristalsis is present at the site of obstruction. Based on this result, the authors conclude that the pacemaker cells may be pressure sensitive. The third patient, a 21-year-old male has a megaureter. In his case poor clearance is paired with hyperperistalsis, therefore peristalsis in the case of megaureters has little effect of excretion.