Proteinuria and Enzymuria in Vesicoureteric Reflux

Effect of chronic, low-pressure, sterile vesicoureteral reflux on renal growth and function in a porcine model: a radiologic and pathologic study

PURPOSE

To study the effects of chronic, low-pressure, sterile vesicoureteral reflux (VUR) on renal growth and function in a porcine model.

MATERIALS AND METHODS

Unilateral VUR was created in five pigs, with the contralateral kidney serving as a control. Preoperatively, and 1 year later, ultrasonography, technetium 99m-dimercaptosuccinic acid (DMSA) scintigraphy, contrast material-enhanced computed tomography (CT), and contrast-enhanced magnetic resonance (MR) imaging were performed. Morphologic abnormalities and relative uptake of (99m)Tc-DMSA were recorded. The postcontrast enhancement ratios for parenchymal regions of interest at CT and MR imaging were determined. Ruthenium 103-labeled microspheres were used to determine regional blood flow. After the pigs were sacrificed, the kidneys were excised, weighed, and analyzed pathologically.

RESULTS

Two of five refluxing kidneys had less than 45% function at scintigraphy. One of these two kidneys was small at postmortem examination. There were no other imaging or gross pathologic abnormalities. There was no significant difference in regional blood flow between the refluxing and nonrefluxing kidneys. In all of the operated on kidneys, histologic examination showed focal chronic inflammation and fibrosis.

CONCLUSION

Low-pressure sterile reflux into previously normal kidneys led to mild, focal, chronic interstitial inflammation and fibrosis after 1 year. Imaging findings were normal apart from a subtle decrease in tubular function in two refluxing kidneys.

Serum levels of IgG antibodies against Tamm-Horsfall protein and urinary excretion of NAG and alpha-1-microglobulin as possible markers for tubular damage in patients with a continent ileal reservoir for urinary diversion

Serum IgG antibodies against Tamm-Horsfall protein and urinary excretion of NAG and alpha-1-microglobulin were measured in 26 patients with a Kock reservoir for continent urinary diversion or orthotopic bladder reconstruction in order to detect any signs of tubular damage. None of these markers for tubular damage was correlated to the postoperative observation time ranging between 2 and 16 years. No correlation was found between these markers and signs of renal scarring or upper urinary tract dilatation as judged from urographies. A positive correlation was demonstrated between NAG excretion and antibodies against Tamm-Horsfall protein. The annual reduction in GFR was increased in patients with elevated alpha-1-microglobulin excretion but not in patients with elevated titres of antibodies against Tamm-Horsfall protein or increased NAG excretion. Patients with previous or present reflux nipple problems had elevated excretion of alpha-1-microglobulin. Regular determinations of alpha-1-microglobulin excretion appear to be of value in the follow-up of these patients.

Renal tubular dysfunction after urinary diversion

Renal tubular function can be assessed by measuring low molecular weight proteins in urine. In the present study, urinary levels of protein HC, also called alpha 1-microglobulin, were determined in 84 patients, 3-17 years after conduit diversion or continent urinary reconstruction. Increased excretion of protein HC, indicating tubular dysfunction, was found in 30 patients (36%), but was slight in most cases. Among patients with GFR > 45 ml/min/1.73 m2 at latest follow-up, the fall from preoperative GFR was greater in those with elevated levels of protein HC than in those with normal levels (p < 0.01). No permeation of protein HC through the intestinal mucosa in contact with urine could be demonstrated. Urinary protein HC may be a suitable marker for detecting early renal impairment after urinary diversion.

Regional renal blood flow measurements using radioactive microspheres in a chronic porcine model with unilateral vesicoureteral reflux

95Niobium labeled radioactive microspheres were used to determine regional renal blood flows in a porcine model of chronic sterile vesicoureteral reflux. Unilateral vesicoureteral reflux was surgically created in 5 mini-pigs and regional renal blood flows were determined by microsphere injection 6 months later. The contralateral nonrefluxing kidney acted as a control. There was a significant reduction of flow in the inner cortical regions of the middle (78% of control, p < or = 0.0437) and lower poles (69% of control, p < or = 0.0274), and the juxta-medullary cortical region of the lower pole (67% of control, p < or = 0.0124). There was no difference in flow in the other regions or when comparing whole kidneys. There were no differences between refluxing and nonrefluxing kidneys when comparing ratios of inner to outer cortical flow level by level. These observations are in contrast to those in acutely created vesicoureteral reflux in a porcine model, which had no significant differences in flow in any region using the microsphere technique. Decreases of blood flow in certain cortical regions may help explain some of the physiological changes in vesicoureteral reflux in children and experimental models of reflux.