Radiologic imaging of the transplanted bowel

The radiologic evaluation of the transplanted bowel is largely unknown and rather complex because it involves several techniques that depend on indications and times that have not been fully defined.

From December 2000 to November 2002 in the Section of Radiology I of the University of Modena and Reggio Emilia (Modena, Italy), 11 patients with transplanted bowel were studied with different methods: traditional radiologic evaluation with contrast agent (all patients), evaluation of transit time with radiopaque markers (five patients), ultrasonographic (US) evaluation of the intestinal wall and Doppler US of the vascular axes (five patients), computed tomographic (CT) evaluation (all patients), and magnetic resonance (MR) evaluation of the bowel and the vascular axes (five patients). Traditional contrast examination enabled evaluation of the gastroesophageal transit and cardia functionality; anatomy and integrity of the anastomoses (proximal and distal); time of gastric emptying; morphology, tone, and kinesis of the transplanted small bowel loops and time of global transit. The study of transit with radiopaque markers was carried out in five patients to define the time of transit through the entire transplanted bowel, confirm recovery of intestinal motility, and identify possible abnormalities. The US examination was carried out in five patients to evaluate the morphology, thickness, and echo structural features of the intestinal loops. Color Doppler was performed to visualize the superior mesenteric artery and a wall arteriole of the sampled loop. CT examination was performed 2 to 4 weeks after surgery to evaluate the anatomy of the transplanted organs, arterial and venous anastomoses in case of complications identified with other methods or suspected, and periodically in the follow-up of patients who underwent transplantation due to Gardner syndrome. The protocol for MR evaluation of the bowel included coronal single-shot fast spin-echo T2-weighted sequences, axial and/or sagittal single-shot fast spin-echo T2-weighted sequences, coronal fast multiplanar spoiled gradient-echo (FMP- SPGR) sequences, coronal FMPSPGR sequences with and without administration of intravenous paramagnetic contrast agent, and axial or sagittal FMPSPGR fat-saturated sequences performed after dynamic gadolinium administration.

The study of transit with radiopaque markers was useful in patients with chronic intestinal pseudo-obstruction because it identified recovery and normalization of motility. Traditional contrast examination of the gastrointestinal tract continues to play an important role in transplanted patients because it is a simple examination that allows evaluation of the graft anatomy and recovery of motility of the residual native bowel and the transplanted loops. Moreover, it plays a crucial role in early detection of major postoperative complications such as intestinal obstruction, perforation, fistulas, and anastomotic complications (stenosis and dehiscence). CT examination is crucial for the detection of fluid collections, abscesses, and fistulas because it can serve as a guide of drainage and during follow-up of patients with Gardner syndrome can be used to investigate all possible sites in which desmoids might arise in addition to their relation to the graft. Because patients with transplanted bowel are generally rather a young population of reproductive age and because of technologic advances, MR may represent an effective method that does not use ionizing radiation and can therefore substitute for traditional radiologic evaluation. US represents a quick examination technique that is easily available and well tolerated by patients, and it has a role to play in the follow-up of transplanted patients and in the identification of major postoperative complications. However, its role in monitoring possible rejection remains to be defined with studies on wider and more representative samples.