Hydronephrosis Resulting from Bilateral Ureteral Stenosis: A Late Complication of Polyoma BK Virus Cystitis?

Development and validation of a risk assessment tool for BKPyV Replication in allogeneic stem cell transplant recipients

BACKGROUND

BK polymavirus (BKPyV), a member of the family Polyomaviridae, is associated with increased morbidity and mortality in allogeneic stem cell transplant recipients.

METHODS

In our previous retrospective study of 2477 stem cell transplant patients, BKPyV replication independently predicted chronic kidney disease and poor survival. In this study, using the same cohort, we derived and validated a risk grading system to identify patients at risk of BKPyV replication after transplantation in a user-friendly modality. We used 3 baseline variables (conditioning regimen, HLA match status, and underlying cancer diagnosis) that significantly predicted BKPyV replication in our initial study in a subdistribution hazard model with death as a competing risk. We also developed a nomogram of the hazard model as a visual aid. The AUC of the ROC of the risk-score-only model was 0.65. We further stratified the patients on the basis of risk score into low-, moderate-, and high-risk groups.

RESULTS

The total risk score was significantly associated with BKPyV replication (P < .0001). At 30 days after transplantation, the low-risk (score ≤ 0) patients had a 9% chance of developing symptomatic BKPyV replication, while the high-risk (score ≥ 8) of the population had 56% of developing BKPyV replication. We validated the risk score using a separate cohort of 1478 patients. The AUC of the ROC of the risk-score-only model was 0.59. Both the total risk score and 3-level risk variable were significantly associated with BKPyV replication in this cohort (P < .0001).

CONCLUSIONS

This grading system for the risk of symptomatic BKPyV replication may help in early monitoring and intervention to prevent BKPyV-associated morbidity, mortality, and kidney function decline.

Urinary polyomavirus: novel biomarker of congenital ureteropelvic junction obstruction

BACKGROUND

Pregnancy is associated with reactivation and transmission of latent polyomavirus to fetus. Polyomavirus is also known to cause ureteral stenosis and hydronephrosis.

OBJECTIVE

The aim of this study was to investigate whether the urinary polyomavirus could be used as a potential biomarker in newborns with ureteropelvic junction obstruction (UPJO).

STUDY DESIGN

Urinary polyomavirus virus was measured by PCR in 42 newborn infants with fetal hydronephrosis history. Random urine samples were obtained from newborns immediately after birth and from their mothers at the time of delivery. Results were compared with 25 healthy infants matched for gestational and postnatal ages. The diagnosis of UPJO was established by diuretic renal scintigraphy. UPJO was graded according to the Society for Fetal Urology (SFU) classification.

RESULTS

The urine samples of healthy infants showed no detectable polyomavirus. No statistically significant difference was found in the median urinary polyomavirus level between grade 1 (1000 copies/mL) and grade 2 (1500 copies/mL) UPJO infants. When the median urinary BKV values were compared for each grade of UPJO, patients with grade 3 and 4 had significantly higher urinary polyomavirus levels than those with grades 1 or 2 (P < 0.001). There was a strong correlation between the median polyomavirus in the urine of pregnant women and the urine of newborns with UPJO (P < 0.001).

DISCUSSION

Data suggest that routine screening of urinary polyomavirus may help to identify infants with severe obstruction in whom early surgical intervention could reduce the risk of developing progressive kidney disease. To the best of our knowledge this is the first prospective study to present the role of urinary polyomavirus in newborn infants with UPJO to distinguish between patients who would benefit from early surgical intervention.

CONCLUSION

Urinary polyomavirus is a potential biomarker of UPJO in newborns with fetal hydronephrosis.

Reversible ureteral obstruction due to polyomavirus infection after percutaneous nephrostomy catheter placement

BK virus (BKV) is a human polyomavirus that remains latent in the urinary tract epithelium in most individuals. However, in immunocompromised states, including after hematopoietic stem cell transplantation (HSCT), BKV may reactivate and cause infection predominantly affecting the bladder, commonly manifested as hemorrhagic cystitis. Renal insufficiency, occasionally requiring hemodialysis, is not uncommon and was previously attributed to medications or the development of tubulointestitial nephritis. We report a series of 6 HSCT recipients who developed obstructive uropathy of the upper urinary tract system secondary to inflammation and hemorrhage involving the upper uroepithelium, causing ureteral stenosis. Temporary placement of a percutaneous nephrostomy catheter relieved the obstruction and significantly improved kidney function, successfully preventing progression to more advanced renal disease in these patients.