Intestinal Failure And Assessment
Intestinal failure means that the patient can no longer maintain their nutritional needs by oral intake of food. In some patients, for example those who have had a recent bowel resection, this is a temporary state that will recover as the residual bowel adapts; in others with very diseased bowel or major resections the condition may be irreversible with a continued requirement for parenteral nutrition (PN).
Parenteral nutrition is the main treatment for patients with intestinal failure. It requires an indwelling central venous catheter to which the patient connects a bag of nutrition (typically 2.5 litres) every evening to run over 12 to 14 hours through the night. Most patients can live a reasonable existence on such therapy.
Complications of parenteral nutrition
The 1-year survival of a patient on home PN is 90%, falling to 65% at 5 years. There are three principal complications of long-term PN.
The central venous catheter may become infected during the course of setting up or taking down the PN infusion, or if the catheter is damaged. Sepsis may remain line-associated or may result in infective endocarditis or other disseminated infection.
Indwelling cannulas are associated with venous thrombosis, with loss of that central vein for future access. Patients predisposed to thrombosis may rapidly lose their internal jugular veins or even thrombose the superior vena cava (SVC), necessitating a cannula in a femoral vein or, via direct translumbar puncture, in the inferior vena cava (IVC). Extensive venous thrombosis may preclude transplanta- tion, so early referral as venous access diminishes is important.
Intestinal failure associated liver disease (IFALD)
Liver disease affects over half of patients on long-term PN, although it may start before PN is instituted in the very malnourished patient. In children, this is commonly due to cholestasis, in adults it is usually steatohepatitis. Steatohepatitis is probably a consequence of the high glucose intake, stimulating insulin production which promotes lipogenesis, combined with high lipid infusions. In both groups the disease may progress to fibrosis and cirrhosis.
Biliary sludge and gallstones are common in both age groups, and is associated with short bowel syndrome in the absence of PN.
Other factors predicting poor outcome on PN
The other factors associated with a poor outcome on PN are age (children, and adults over 60); extremely short length of residual bowel (<50 cm); dysmotility disorders; radiation enteritis; and longer duration of treatment.
Indications for transplantation
Intestinal transplantation is indicated for one of three main reasons.
1. Complications of parenteral nutrition (PN):
· PN-induced liver injury;
· thrombosis of two or more central veins;
· two or more episodes of catheter-related sepsis per year requir- ing hospitalisation;
· a single episode of fungal catheter-related sepsis; septic shock;
· frequent severe dehydration due to gut losses despite intravenous fluid supplementation and PN.
2. Requirement for major gut resection for tumour, such as a desmoid tumour invading the mesentery.
3. Unacceptable quality of life on PN.
Assessment for transplantation
There are three main aspects to the assessment of intestinal transplant recipients.
Fitness for surgery
Multivisceral transplantation is akin to liver transplantation in its surgical stress. Full cardiological and respiratory assessments are performed. Since kidney failure is common post-intestinal trans- plantation and is difficult to assess in patients on PN, a nuclear medicine glomerular filtration rate (GFR) measurement is required to gauge the need for simultaneous kidney transplantation.
Extensive venous mapping is usually required to identify sites for peri-operative access. The presence of SVC thrombosis is a contraindication to a liver transplant using a classical caval replacement technique, because this would remove all venous return to the heart. At least one femoral vein needs to be patent, with patency of the IVC.
A preferred site for a stoma should be marked, and the patient should receive appropriate stoma counselling.
Patients undergoing modified or full multivisceral transplantation will undergo splenectomy as part of the explant procedure. They should therefore be immunised against meningococcus, pneumococcus and haemophilus influenza before listing.
Extensive psychological assessment is required, particularly of anyone undergoing the procedure only for quality-of-life.
Is there any evidence of underlying liver disease? Imaging, including duplex ultrasound of the liver, and liver biopsy are usually required in addition to liver biochemistry to assess whether the liver is affected by IFALD, and if so, whether it needs replacing.
Previous surgical history detailing any and every resection is important to enable judgement as to what is feasible. This is supplemented by contrast imaging of the remaining bowel, together with endoscopic inspection of any bowel to be left in situ to exclude disease, and also inspection of any bowel to be removed to confirm the diagnosis if required.
Three-dimensional imaging of the gut is particularly important in the case of malignancy to allow estimation of the extent of the tumour. Desmoids, the commonest malignancy for which trans- plantation is undertaken, are associated with intestinal polyposis (Gardner syndrome) and usually arise within the mesentery and extend to the adjacent structures, such as the abdominal wall, renal tract or great vessels in the retroperitoneum. All residual tumour should be removed.
Results of intestinal transplantation
Outcomes following intestinal transplantation vary, and are better in centres with high-volume programmes, in younger recipients and in patients transplanted from home rather than in those who were inpatients already. Overall graft survival rates are around 80% and patient survival rates are around 90% at 1 year.