Uses of the radioisotope renogram with emphasis on evaluation of ureteropelvic junction obstruction

Ureteropelvic Junction Obstruction: Some new Acquisitions about Etiology, Pathophysiology and Diagnostics

The etiopathogenesis of uretero-pelvic junction obstruction (UPJO) has been the subject of many speculations and it remains, in some ways, a debatable matter. Some recently reported thorough research refer to neuro-mediated pathogenetic mechanisms rather than (or together with) myogenic ones.

Advances in US, radioisotopic functional imaging, CT and RM contribute to differentiate the obstructive conditions from the non-obstructive ones and to afford today a better assessment of renal functional damage. Particularly, diuretic renography is a non-invasive test for characterization of the renal functional abnormalities resulting from UPJO. Helical CT with angiography is a useful technique for identification of crossing vessels (pyelo-vascular tangle) which can be used for the pre-surgical planning of endopyelotomy. Endoluminal ultrasonography can be used to guide the position of the incision for endopyelotomy (US-guided endopyelotomy).

Laboratory examinations are important to determine the overall renal function (serum creatinine, acid-base balance, serum electrolytes, etc.), urinary MCP-1 and NAG (markers of tubular damage), and to rule out urinary tract infections.

The management of UPJO (watchful waiting; either open or laparoscopic dismembered pyeloplasty; endoluminal procedures) is greatly influenced by the diagnostic evaluation.

The paper aims to outline the advances in both physiopathology and diagnostics of UPJO on the basis of a review of the literature.

Radionuclides in the evaluation of urinary obstruction

Radionuclide renography and renal scanning techniques are ideally suited to the initial and follow-up evaluation of patients with obstructive uropathy. While other modalities are superior in their ability to provide anatomic information, the radionuclide study yields functional information for each kidney without the necessity to resort to invasive studies. In addition, the Nuclear Medicine study is well suited to the evaluation of obstruction where serial studies often are required because of a lower radiation burden compared to urography. This lower radiation dose is especially important in obstruction because of the recurrent nature of several kinds of obstructive uropathy and because of the high incidence in the pediatric age group. The ability to control urine flow rate during the procedure through dehydration or administration of diuretics is an additional benefit. Increasing availability of computerization of nuclear medicine procedures as well as interest in studies employing physiologic intervention (including the diuresis renogram) have assured an important place for radionuclide studies in the evaluation of patients with urinary obstruction.

Diuresis renography and the results of pyeloplasty for idiopathic hydronephrosis

Eighty-six kidneys in 82 patients have been assessed by diuresis renography after pyeloplasty. A non-obstructed diuresis renogram was found in 64% of kidneys. Ninety per cent of patients were clinically improved by surgery and 51% of cases studied had improved urographic features. Thirty kidneys (29 patients) were assessed both before and after pyeloplasty. An improvement in the diuresis renogram was found in 89% of cases postoperatively. Standard renography demonstrated improved drainage in only 33% of kidneys. These findings are discussed in relation to the value of diuresis renography after pyeloplasty.

Idiopathic hydronephrosis--the diuresis renogram: a new non-invasive method of assessing equivocal pelvioureteral junction obstruction

A new method to evaluate patients with equivocal obstruction of the pelvioureteral junction is described. It involves the performance of a standard 131iodine-hippuran renogram followed by a second renogram 3 minutes after an intravenous injection of the diuretic, frusemide. When the 2 results are inspected together it is found that the patients can be separated into 4 groups: 1) normal, 2) obstructed, 3) atonic and 4) partially obstructed. The results in 23 children and 27 adults with suspected obstruction of the pelvioureteral junction are presented. Obstruction was confirmed in 18 patients and excluded in 32. The correlation between the renogram results and clinical, radiological and operative findings is discussed. The technique is simple, accurate and non-invasive, and it is recommended after excretory urography before proceeding to more invasive tests.

Diuresis renography in equivocal urinary tract obstruction

A trial of the value of diuresis renography in equivocal upper urinary tract obstruction is presented. Fifty-two patients were examined by standard renography and renography under a diuretic provocation. The results indicate that the technique is of considerable value in making the vital distinction between dilatation on the excretion urogram due to atonicity and that caused by a genuine obstruction. A quantitative index of the response to diuresis reflecting the degree of impedance to flow is described--the Diuresis Excretion Index. Diuresis renography is recommended in the evaluation of the patient with equivocal urinary tract obstruction.

Efficacy of medical treatment of schistosomal obstructive uropathy as determined by 131I-Hippuran renography

Ten male patients with obstructive uropathy secondary to Schistosoma haematobium and with associated bacteriuria were evaluated with serial urograms, renograms and renal function tests (endogenous creatinine clearance, maximal urinary concentration and total hydrogen ion excretion) before and after medical treatment. The mean duration of follow-up was 4.2 months. Significant improvement was observed in the renograms and the renal function tests while the degree of obstructive uropathy as determined by urography remained essentially unchanged. Thus the renogram can be a more sensitive test for evaluating the efficacy of treatment in patients with schistosomal obstructive uropathy.

Hydronephrosis. Assessment of late results after treatment of pelvi-ureteric junction obstruction

Hydronephrosis is probably caused by a muscular anomaly at the pelvi-ureteric junction. A pyeloplasty technique involving the resection of this anomalous portion has been generally recommended. However, this study shows that procedures which preserve the anatomical continuity might also lead to excellent late results. The immediate postoperative complications were few and minor, and the low incidence of complications was partly the result of the splinting technique, which is therefore recommended. A scheme for evaluation of late results is suggested.