The potential donor should be an individual in good health with no history of previous intestinal or abdominal surgery, and with no underlying chronic medical illnesses that would increase the surgical operative risk.

Once a potential donor is identified, the initial step should consist of a meeting with the surgeon to describe the procedure, as well as risks and benefits and the steps involved in the workup. During this initial visit, the potential donor can be screened with an ABO blood type determination. If this is compatible and the candidate is willing to continue the workup, an HLA test and histocompatibility testing by T-cell crossmatch should be performed. Crossmatch should be negative, and among multiple donor candidates, the one with the best HLA match should be preferred and should be directed to continue the workup. The cornerstone of success is the identical or compatible HLA. For this reason, it is preferred that living donors be relatives of the recipients. The donor can also be unrelated to the recipient but should have a compatible HLA and close emotional relationship. This condition and the absence of any financial interest or coercion for donation are of paramount importance in LD-ITx, just like any other type of live organ donation. The screening process should exclude active or uncontrolled psychiatric disorders, and ensure the altruistic nature of the donation. The institution’s ethical committee should separately evaluate the donor to ensure that there is full understanding of the limited information regarding the short- and long-term risks associated with intestinal donation.

Once the potential donor has completed these initial steps, a series of tests are mandatory for the live donor evaluation (Table 4.3). Based on the available clinical experience with LD-ITx, a limit of 60 years of age is advisable. The minimal age is only determined by legal ability to consent to the procedure. High body mass index (> 30) may not affect graft quality and does not constitute, per se, an absolute contraindication to live donation, though general surgical experience indicates that a high body mass index (> 30 kg/m²) may increase the risk of surgical complications after intestinal resection.

A comprehensive metabolic panel should be obtained. Blood test results that confirm donor infection with HIV, HCV, or HBV are contraindications for living intestine donation.

Specific considerations must be used for genetically related donors of potential recipients who have a genetic or familial intestinal disease. Despite the fact that no data are available at this time, it is possible that the related donor might develop the same condition later in life. At the present time, it is advisable not to consider these donors and eventually to screen them to rule out the same genetic disorder.

Imaging studies are performed to rule out underlying or occult pathology and to specifically delineate the intestinal vascular anatomy. A computed tomography (CT) or magnetic resonance (MR) angiography is performed, possibly with computerized three-dimensional (3D) reconstruction, if available. In case, these techniques are not available or are inadequate, a traditional angiogram can be also performed. Angiography is performed to evaluate the superior mesenteric artery (SMA) anatomy, to ensure a normal vascular distribution to the small bowel with particular attention to the right colic and ileocolic arteries and the terminal branches of the SMA, and to exclude the presence of atherosclerotic disease and abnormal anatomy. If more than one donor is available, patients with a single distal arterial pedicle should be preferred to patients with multiple vessels. These vessels usually originate caudal to the takeoff of the right colic artery and must be spared during procurement to provide adequate blood supply to the cecum, terminal ileum, and ileocecal valve (Fig. 4.3).

TPN-induced cholestasis is a condition of impaired canalicular secretion of bile, characterized by bile duct regeneration, portal inflammation, and fibrosis. It is diagnosed in patients receiving TPN who develop cholestasis not due to other liver diseases or biliary obstruction. The clinical manifestations include elevated serum bilirubin and/or liver enzymes, splenomegaly, thrombocytopenia, gastroesophageal varices, coagulopathy, stomal bleeding, or hepatic fibrosis/cirrhosis. Its progression could be very rapid, and in some patients, liver cirrhosis may develop in a few months [30].

This can be consequent to the thrombosis of the major central venous system, such as jugular, subclavian, and femoral veins. Thrombosis of two or more of these vessels is considered a life-threatening complication and a failure of TPN therapy. The sequelae of central venous thrombosis are the lack of access for TPN infusion, fatal sepsis secondary to infected thrombi, pulmonary embolism, superior vena cava syndrome, or chronic venous insufficiency.

The development of two or more episodes per year of systemic sepsis, secondary to line infection that requires hospitalization, also indicates failure of TPN therapy. A single episode of line-related fungemia, septic shock, and/or acute respiratory disease syndrome (ARDS) is considered TPN failure.

Under certain medical conditions, such as secretory diarrhea, in GI tract that cannot be reconstructed, the loss of the GI and pancreatobiliary secretions exceed the maximum intravenous infusion rates that can be tolerated by the cardiopulmonary system.

It is imperative to know the anatomy of the recipient pretransplant. If numerous intestinal resections have been performed over a long period of time, often previous medical records are not available or are inaccurate in recording the remaining portion of the intestine and its length after each surgery. In addition, intraoperative evaluation of the anatomy is often difficult due to the scarring and adhesions found. Upper and lower GI series with contrast will allow one to visualize the portion of residual gut, its position in the abdominal cavity, and its length. It is not uncommon that during a workup, a longer-than-expected segment of small or large intestine is identified, and this might allow different strategies than transplantation, such as surgical recanalization of the residual intestine, intestinal rehabilitation, or other surgical elongation procedures. Abdominal CT scan (or MR imaging) with contrast is also used to rule out malignancies or other undiagnosed diseases.

Patency of the upper and lower body veins must be established by venogram, since duplex scan might not be sufficiently sensitive for this purpose. Thrombosis of these vessels is not uncommon in patients receiving TPN. Thrombosis can cause inability to cannulate the vessels, and can cause superior vena cava syndrome when the inferior vena cava (IVC) is clamped. The patient may have patency only of the femoral veins. Complete lack of venous access could be a contraindication for ITx.

Electrocardiography and echocardiogram are used to determine the cardiac function and any valvular lesions, and should be accompanied by a cardiologic evaluation and clearance for surgery. Stress test or cardiac catheterization may also be performed, if indicated.

Liver biopsy may be indicated in patients with intestinal failure and hepatic dysfunction. TPN-induced cholestatic liver injury can be reversed by isolated intestinal transplant or by restoring intestinal integrity [31]. However, in the presence of liver cirrhosis or portal hypertension, a patient with intestinal failure requires a combined liver–ITx. This can be performed using a deceased donor. However, as an option, liver transplant from a deceased donor can be followed by intestinal transplant from a living donor, if an intestinal graft is not attainable from the same donor at the same time. In addition, in pediatric patients, combined liver–ITx from a living donor has been recently reported [10].

Further assessment of associated liver disease (portal hypertension, coagulopathy, ascites, hyperdynamic circulation, hepatopulmonary syndrome, and hepatic encephalopathy) should be done, if indicated.

Patients with familial polyposis should be evaluated for the presence of polyps in the remaining portion of the Gl tract. Patients with dysmotility disorders may require an assessment of the stomach to evaluate functional abnormalities. Children with pseudo-obstruction may require urologic assessment because as many as a third may have a dysfunctional urinary tract. Children with necrotizing enterocolitis may require a full neurologic and pulmonary workup to exclude the possibility of associated intraventricular hemorrhage and bronchopulmonary dysplasia.

The transplantation of an intestinal graft from a live donor, by definition, involves the transplantation of a segment of the small intestine. Central caveat of the donor operation is to provide adequate length of intestine to the recipient to ensure enteral autonomy, while preserving enough small bowel length in the donor. The appropriate length and the anatomic origin of the segmental graft to harvest is the cornerstone of a successful transplant.

The arterial blood supply to the small intestine is from the superior mesenteric artery (SMA) . The basic pattern of distribution of the intestinal arteries generally includes 5 arteries arising on the left of the SMA above the origin of the ileocolic artery and 11 below that level. Eight additional arteries usually originate from the ileal branch of the ileocolic artery [32]. These intestinal vessels branch a few centimeters from the border of the intestine to form arterial arcades connecting the intestinal arteries with one another. Proximally, a single set of arcades is present; distally, there are usually several sets of arcades. These arches form the primary interconnections of the arterial supply. From arches and arcades, the vasa recta arise and pass without cross-communication to enter the intestinal wall. A complete channel may also exist from the posteroinferior pancreaticoduodenal artery that is parallel to the intestine and joins the marginal artery of Drummond of the colon. The terminal ileum, ileocecal valve, and right colon receive blood supply also from the right colic artery and ileocolic artery, often sharing a common origin, connected by the marginal artery of Drummond to the terminal branches of the SMA (Fig. 4.6). In 5 % of the population, blood supply to these structures is guaranteed only by the ileocolic artery, as the marginal artery is incomplete (Fig. 4.7). The venous drainage of the small intestine is less complex than the arterial vessels, merging in the jejunal and ileal veins, and into the superior mesenteric vein and portal vein.

From a technical standpoint, the ileum offers the advantage of a larger vascular pedicle if the distal portion of the SMA is used. This vessel can be transected below the takeoff of the right colic artery to avoid hypoperfusion of the terminal ileum, and the preservation of the ileocecal valve in the donor (Fig. 4.8). At this level, this artery is commonly single, but could also consist of two or more branches. Additionally, despite the fact that both jejunum and ileum have the ability to adapt following intestinal resection, the ileum has the advantage of allowing structural and functional adaptation [33, 34].

Despite these advantages, the jejunum has been also used in early experience for the possible immunologic advantages, since it has been reported, from small-animal studies, that acute rejection is less severe in the jejunum [35, 36]. However, the vascular distribution to the jejunum makes the operation more complex, as the segmental graft obtained has numerous arterial branches needing multiple anastomoses in the recipient to obtain adequate revascularization for the graft (Fig. 4.9). Jaffe et al. reported attempts at proximal small bowel transplantation involving complex vascular reconstruction that resulted in vascular complications [35]. In addition, the early clinical experience from the same group did not show a clear immunologic advantage with the use of jejunal segmental grafts.

The appropriate length of the human alimentary tract to be resected has proven to be surprisingly difficult to measure. The length of the small intestine in deceased donors was reported to be from 10 to 40 feet, with an average of 20.5 feet or 624.8 cm [37]. In vivo measurements using an intraluminal method provided an average of 8.5 feet or 258 cm [38]. This discrepancy is attributed to the postmortem loss of longitudinal muscle tune of the small intestine that can lead to an increase in length, up to 135 % in a few hours, as shown in animal studies [39]. For the purpose of ITx, intestinal measurements are performed in a live subject, but being under general anesthesia, the effect of the pharmacologic agents used might affect the intestinal distension, motility, and length [40–43].

For these reasons, the calculation of a generic optimal length of small bowel graft to resect can be difficult. In each individual case, the entire small bowel should be measured from the ligament of Treitz to the ileocecal valve, using a sterile surgical tape. Once the length of the entire small bowel is determined in a particular patient under a specific anesthetic agent, a final determination of the segment to be removed is made. Although it is relatively easy to determine when an intestinal segment is too short, the long-term impact to the donor of the resection of a longer segment is unknown. Deltz reported a transplant of a 60-cm segment of distal jejunum and proximal ileum, whereas, Morris used a similarly long segment of distal ileum, ileocecal valve, and a portion of the cecum [44, 45]. Despite these early successes, a length of 60-cm small bowel has been generally inadequate to provide a TPN-free condition [44], and resection of the ileum, ileocecal valve, and cecum can have a negative impact on the function of the remaining donor bowel (e.g., increased transit time and vitamin B₁₂ deficiency) [45].

From the short-bowel syndrome literature, a segment of approximately 1 m has been reported to be sufficient to ensure adequate absorption [29]. However, this depends on the presence of the ileocecal valve or part of the colon. Considerations in the recipient anatomy also play an important role in determining the length of the intestinal segment to remove in the donor. A recipient with no colon or ileocecal valve, for example, will require a longer segment compared with a patient where these structures are present.