Standardized Ileal Bladder Augmentation For Enterocystoplasty In Rats via Midline Laparotomy

Alexander Studier-Fischer; Lasse Maywald; Paula Grützner; Berkin Özdemir; Caelan Max Haney; Samuel Knoedler; Luisa Renner; Nicolas Carl; Tilmann Clanget; Gabriel Alexander Salg; Niklas Westhoff; Maurice Stephan Michel; Karl-Friedrich Kowalewski

doi:10.3791/71123

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Method Article

Standardized Ileal Bladder Augmentation For Enterocystoplasty In Rats via Midline Laparotomy

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DOI:

10.3791/71123

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June 12th, 2026

Alexander Studier-Fischer^*¹^,²^,³^,⁴ , Lasse Maywald^*¹^,³^,⁴ , Paula Grützner¹^,³^,⁴ , Berkin Özdemir²^,³^,⁴ , Caelan Max Haney²^,³^,⁴^,⁵ , Samuel Knoedler⁶ , Luisa Renner¹^,³^,⁴ , Nicolas Carl¹^,⁷ , Tilmann Clanget¹ , Gabriel Alexander Salg² , Niklas Westhoff¹ , Maurice Stephan Michel¹^,³^,⁴ , Karl-Friedrich Kowalewski¹^,³^,⁴

¹Department of Urology and Urosurgery, University Medical Center Mannheim, Medical Faculty of the University of Heidelberg, ²Department of General, Visceral, and Transplantation Surgery, Heidelberg University Hospital, ³Division of Intelligent Systems and Robotics in Urology (ISRU), German Cancer Research Center (DKFZ) Heidelberg, ⁴DKFZ Hector Cancer Institute at the University Medical Center Mannheim, ⁵Department of Urology, University Hospital Leipzig, ⁶Department of Plastic Surgery and Hand Surgery, TUM University Hospital Munich, ⁷ORSI Academy, Innotech

^* These authors contributed equally

Summary

This protocol describes a standardized rat enterocystoplasty model using a pedicled, vascularized, and detubularized ileal patch with temporarily externalized urinary diversion via a cannula tube to achieve reproducible bladder augmentation.

Abstract

Bladder augmentation using intestinal segments remains a cornerstone reconstructive procedure for patients with low-capacity or poorly compliant bladders when conservative therapies fail. Despite its clinical relevance, experimental progress and in-depth study are limited by the lack of standardized, reproducible protocols that reliably model surgical principles in a controlled preclinical setting. Here, we present a step-by-step rat enterocystoplasty protocol that uses a vascularized, detubularized ileal patch as a pedicled flap to augment the native bladder. The procedure includes midline laparotomy, controlled exposure, and stabilization of the bladder with holding sutures, urinary diversion via an exteriorized cannula tube Foley, isolation of a short ileal segment with an intact mesenteric pedicle, detubularization, and tension-free anastomosis with the bladder wall. Emphasis is placed on maintaining mesenteric perfusion, preventing pedicle torsion, ensuring watertight suturing, and securing catheter patency, which are critical for procedural success and reproducibility. Representative intraoperative validation using hyperspectral imaging (HSI) in eight non-survival rats demonstrated preserved tissue oxygenation and perfusion of the bowel segment after key operative steps, supporting tissue viability at the end of this procedure. Thus, this protocol provides a standardized experimental approach for reproducible surgical implementation of rat enterocystoplasty. Potential downstream applications of the model include the investigation of metabolic and electrolyte alterations, infection susceptibility, mucus production, and induction of dysplasia or malignancy, and remain to be addressed in future survival investigations.

Introduction

A physiological urinary bladder function is fundamental to maintaining a high quality of life, as effective urine storage and voiding are critical for continence, social well-being, and overall health. Disorders affecting bladder function can result in substantial morbidity, including urinary incontinence, recurrent infections, renal impairment, and a profound negative impact on daily life.

Both congenital and acquired bladder pathologies can cause significant functional impairment, often necessitating surgical intervention when conservative and pharmacological treatments prove insufficient. Congenital anomalies such as posterior urethral v....