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Abstract: SA-PO1097

Extensive Tubular Ectasia Indicating Occult Urological Obstruction in Renal Allografts

Session Information

Category: Pathology and Lab Medicine

  • 1502 Pathology and Lab Medicine: Clinical


  • Bojic, Marija, Medical University of Vienna, Vienna, Austria
  • Regele, Heinz, Medical University of Vienna, Vienna, Austria
  • Seitz, Christian, Medical University of Vienna, Vienna, Austria
  • Kikic, Zeljko, Medical University Vienna, Vienna, Austria

Urological obstructive complications (UOC) affect up to 10 % of kidney transplantation (KTX) cases. The majority of the cases may be excluded by routine ultrasound (US), however its accuracy may be limited in the early transplant setting. Renal allograft biopsy (BX) may be valuable, but histological features indicating UOC are ill defined. Experimental data suggest that extensive tubular ectasia (TE) may be indicative of OUC. In our center, occult UOC is suspected when tubular ectasia (TE) occurs together with one or more of the following distinct features: acute tubular injury, tubular protein casts and tubular vacuolization. In this study we aimed to assess their accuracy for UOC.


We included 976 of 1537 consecutive KTX with an early indication BX. Relevant hydronephrosis (HN) was excluded by routine US. The bioptical finding of TE suspicious of UOC by the renal pathologist was compared to clinical endpoints as delayed graft function (DGF) and occurrence of UOC. Thereafter, all biopsies initially classified as suspicious for UOC were reevaluated by a single pathologist (H.R.) in order to increase accuracy of histomorphology suggestive of UOC.


Fifty eight (5.9%) presented with TE indicative of UOC which was associated with a higher rate of DGF (40% vs. 29%; p=0.08) and was not related to long-term graft loss. Out of these, 23 (39.7%) had UOC, (most frequently ureteral stenosis) close to BX. To assess the relevance of TE as a marker of UOC without relevant HN, cases with TE were then subsequently compared to matched controls. Solely TE was significantly associated with an increased risk for UOC [OR 2.69 (IQR: 1.19 – 6.09); p = 0.018]. For histopathological reevaluation of the 58 cases, we defined extensive TE (>20% of the renal cortex). Subsequently, a score including additional histological criteria (tubular injury, tubular protein casts and tubular vacuolization) was developed: AUC 0.705, p=0.012. Using a threshold of 1.5, we observed 91% sensitivity, 37% specificity and a 84% negative predictive value.


Occult UOC may be identified in up to 40% of the cases by subtle histopathology including extensive TE together with additional signs of tubular injury. This phenotype should trigger more detailed evaluation for UOC when there is no evidence of relevant HN in the ultrasound.