Clinical Application of Upper Urinary Tract Dynamics

(99m)Tc-DTPA diuretic renal scintigraphy in cats with nephroureterolithiasis

The purpose of this study was to evaluate results of diuretic renal scintigraphy in 32 feline kidneys with nephroureterolithiasis and variable degrees of renal pelvis/ureteral dilation. Six kidneys showed a non-obstructive scintigraphic pattern, with a downward slope of time-activity curves (TAC) and a median excretion half-time of radiopharmaceutical (T((1/2))) of 6.09 (5.08-8.43) min. Eight kidneys showed an obstructive pattern, with a continuous rise of TAC and median T((1/2)) of -7.91 (-43.13-0.00) min. In one kidney with presumptive partial obstruction scintigraphic results were equivocal. Seventeen kidneys, most of which had an individual kidney glomerular filtration rate below 0.5ml/min/kg, had non-diagnostic studies. Diuretic renal scintigraphy may be a useful adjunct modality in the diagnosis of ureteral obstruction in some cats if renal function is maintained. However, the large number of non-diagnostic studies in animals with decreased renal function represents a clear limitation of the technique.

Acute urinary tract obstruction. Imaging update

Although urinary tract obstruction is an age old problem with IVU the time-honored imaging technique of choice, recent advances in renal ultrasonography and abdominal and pelvic CT scanning have advanced these alternative modalities to the forefront. No rigid algorithm for renal obstruction is recommended, because the utilization of these techniques is in a state of flux. The use of one modality over another as a first-line imaging technique likely will depend on the equipment availability and expertise of a given institution. The choice also may be guided by each institution's cost of each type of examination. Although a role for the IVU remains in the evaluation of acute renal obstruction, ultrasonography and CT scan have emerged as alternative primary screening tools. Undoubtedly, the future will bring further changes in our assessment of renal obstruction. The cost effectiveness and definitiveness of evaluation likely will become more important driving factors than they have been in the past. The radiologist and urologist together must assess available imaging techniques, their effectiveness, and the institution's expertise to develop a cost-effective and efficient system for assessment of renal obstruction.

Contemporary concepts for imaging urinary tract obstruction

Ultrasound is an integral tool in the contemporary assessment of urinary tract obstruction. Pulsed and color Doppler have eliminated many previous false-positives due to blood vessels or non-obstructive hydronephrosis. Limitations of the ultrasound technique still exist and on occasion necessitate the utilization of intravenous urography.

Pediatric urinary diversion and undiversion

Many things have changed in our management of the urinary tract of children and young adults. Important contributions from many sources have resulted in the refinement of therapy and the progression from diversion to undiversion and reconstruction. Primary urinary diversion is now uncommon. Patients with exstrophy, for example, are treated with primary bladder closure as newborns, and newborns with valves often are treated with primary valve ablation. Children with neurogenic bladder dysfunction resulting from myelodysplasia are rarely diverted, but are started at an early age with ICC. It is hoped that in future the contents of this article on diversion techniques and undiversion will be of historical interest, however. Note: The editors also have found the use of the Mitrofanoff procedure, utilizing a nonrefluxing tunnel and a catheterizable stoma made out of the ureter or appendix, to be a very valuable addition to the reconstructive surgeon's armamentarium. We also feel that use of detubularized bowel for either bladder augmentation or replacement provides more efficient storage capability. Occasional reports of extremely significant diarrhea after removal of the ileocecal segment from the intestinal tract have been reported in children with myelodysplasia.