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Abstract: PO2259

Is the Well-Recognized Intravascular Tamm-Horsfall Protein Polyp a Misnomer? A Case Report from a Patient with Obstructive Uropathy and Hematuria

Session Information

Category: Trainee Case Report

  • 1602 Pathology and Lab Medicine: Clinical

Authors

  • Suo, Liye, University of Texas Health Science Center at Houston, Houston, Texas, United States
  • Meissner, Kyle, University of Texas Health Science Center at Houston, Houston, Texas, United States
  • Musa, Amal, University of Texas Health Science Center at Houston, Houston, Texas, United States
  • Reddy, Vikas D., University of Texas Health Science Center at Houston, Houston, Texas, United States
  • Teakell, Jade M., University of Texas Health Science Center at Houston, Houston, Texas, United States
  • Glass, William F., University of Texas Health Science Center at Houston, Houston, Texas, United States
Introduction

Tamm-Horsfall protein (THP), a renal epithelial glycoprotein, was originally isolated from normal urine and can be the primary constituent of many urinary casts. The phenomenon of THP polyp formation in obstructive uropathy first appears in the literature about 1978. The polyps are described in these reports as being located in veins or sometimes lymphatics. Our case is the first to confirm the location of a THP polyp by immunohistochemical (IHC) analysis.

Case Description

A 64-year-old Caucasian male presented with bilateral flank pain and persistent gross hematuria. On admission, he had mildly elevated BUN (26.0 mg/dL) and serum creatinine (3.2 mg/dL). Urine analysis showed red blood cells > 182 /hpf with negative leukocyte esterase and negative nitrates. He developed azotemia during the hospitalization with the highest creatinine of 7.4 mg/dL on day 3 of admission. Renal ultrasound indicated mild-moderate hydronephrosis with a collapsed bladder. Renal biopsy was performed given lack of proper explanation for his presentation. Biopsy showed Periodic acid-Schiff (PAS) positive THP with polyp formation distended the markedly dilated tubules (confirmed by positive Pan-cytokeratin and negative CD31 immunohistochemical (IHC) stains). The THP polyp also contains delicate elongate-appearing endothelial cells. There was diffuse interstitial edema with mild fibrosis without tubular atrophy, and mild to moderate to focally intense inflammation with numerous eosinophils surrounding the involved tubules. The walls of the inflamed tubules are densely infiltrated by inflammatory cells and has focal fibrinoid necrosis. No significant glomeruli or vascular pathologic changes were identified. The renal pathology findings of acute to subacute tubulointerstitial nephritis with THP polyps consistent with obstructive uropathy.

Discussion

There were a total of four cases of intravenous THP polyps identified in the patients with obstructive uropathy and persistent gross hematuria. It was theorized that acute hydronephrosis may increase the intratubular pressure, with extravasation of THP into the veins forming tubulovenous communications. However, our study suggests that this theory may not be true due to the misidentification of the markedly distended renal tubules as renal veins.