The Pediatric Short Bowel State: Practical Concepts Toward Enteral Autonomy



Fig. 28.1
Midgut volvulus complicating malrotation and mesenteric non-fixation



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Fig. 28.2
Gastroschisis with extruded bowel on a narrow-based mesentery


Postnatal necrotizing enterocolitis (NEC) and its attendant surgery account for the greater proportion of the remainder (Fig. 28.3). Whereas it is not presently possible to prevent intrauterine bowel loss, a high index of suspicion will reduce postnatal midgut volvulus, while cautious feeding in premature babies and earlier pre-necrosis bowel-preserving surgery for NEC will salvage greater lengths of functional bowel.

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Fig. 28.3
Neonatal necrotizing enterocolitis

Intestinal failure (IF) can be regarded as the inability to sustain survival and growth because of inadequate absorption from the available autologous bowel. Most children with PSBS who suffer from IF have a residual mucosa that is healthy, but is of insufficient amount and of inappropriate configuration. Survival following major loss of absorbing bowel depends on the natural adaptation response [1, 2] that includes bowel elongation and dilatation with a major increase in absorptive brush border surface area consequent on mucosal hypertrophy (increase in villus height) and villus cellular hyperplasia (increased numbers of cells per villus). It is noteworthy that the ileum develops a greater adaptation response and is preferable to the jejunum also because of its specific absorption sites for vit B12 and bile salts. The ileocecal valve (IC valve) is helpful in delaying transit, thereby increasing mucosal contact time for absorption. Greater lengths of the colon are relevant to fluid and electrolyte absorption, with particular advantage for the right colon as the site of production of glucagon-like peptide 2 (GLP-2), an intestinotrophic mediator that is the most potent stimulator of small bowel mucosal adaptation.

Prior to total parenteral nutrition (TPN) and bowel reconstruction, minimum lengths of 40–60 cm of small bowel with an IC valve and the colon were considered necessary for survival. However the length of small bowel compatible with independent survival is markedly influenced by the type, configuration, and health of the residual bowel. TPN, a better understanding of PSBS, and improved techniques for bowel management have increasingly offered hope of enteral autonomy with acceptable quality long-term life, even to patients with extreme short bowel. Patients who have no functional bowel, who have failed autologous bowel management, who have poor quality life, and those who have lost venous access or suffer irreversible liver failure have the option of small bowel-colon or liver-bowel transplantation, with improving long-term outcomes. However, graft rejection and the infective and neoplastic risks associated with immunosuppression remain significant. Furthermore, the constant need for monitoring for acute rejection and the insidious onset of chronic rejection with loss of graft function impacts on quality of life, such that transplantation should not be the first choice but a welcome final resort.



28.2 The Pediatric Short Bowel State


Antenatal midgut volvulus with loss of the superior mesenteric vascular territory presents as a high jejunal atresia (Fig. 28.4) with an occluded dilated loop of the jejunum commonly of 20–40 cm (<10 % of normal) measured from the ligament of Treitz along the antimesenteric border, and an atrophic left transverse colon through to the anus. This residual bowel is usually peristaltic and absorptive with adaptive potential.

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Fig. 28.4
30 cm residual jejunum following antenatal midgut loss

Postnatal midgut volvulus and NEC present as life-threatening peritonitis from ischemic and inflamed bowel and bacterial sepsis. The length and variety of the residual bowel will depend on the extent of the disease, the timing of surgery, and the degree of bowel conservation practiced by the surgeon. The residual proximal and distal bowel are not dilated and are of similar caliber. Significantly, surviving bowel after NEC may not be functionally normal, also having a reduced adaptive potential.

The “lucky” patient with long-segment jejunal aganglionosis (Hirschsprung’s disease) may have a variable length of ganglionic jejunum that is usually of normal function and adaptive potential. All aganglionic bowel distal to the transition zone is aperistaltic and nonabsorptive but should not be removed unless it is the source of infection, since it serves to retain abdominal cavity volume that is relevant to an eventual bowel transplant.

Conventional atresia management with a high jejunal stoma on the abdominal wall or by similar caliber jejunocolic anastomosis is followed by rapid transit and severe loss of fluid, electrolytes, and nutrients. Anastomosis of the markedly dilated proximal jejunum in intestinal atresia, to the smaller diameter distal bowel, is contraindicated since it leads to a “functional obstruction,” with failure of propulsion across a patent anastomosis despite active peristalsis (Fig. 28.5). Stasis within the dilated loop generates bacterial overgrowth with D-lactic acidosis, mucosal inflammation, and bacterial translocation causing liver injury and septicemia. If left untreated, the short bowel state is rapidly fatal from dehydration, malnutrition, and sepsis. TPN offers hope of long-term patient survival with reasonable quality of life and opens the way to autologous bowel rehabilitation and reconstruction and, when all else fails, to transplantation.

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Fig. 28.5
Functional obstruction following a “big-to-small” anastomosis


28.3 The “Hub and Spoke” Model


At an annual incidence of around 1:15,000, the short bowel state in children is of significant impact. Survivors on TPN require intermittent specialist hospital care and long-term home support that places a major burden for dedicated and expensive management on patient’s families and on health service providers. It is essential for long-term care to be delivered close to the family home and local community, allowing easier access to the child for better integration within family and social life and for keeping the family unit within their established work, school, and social environment. Management is best guided from a dedicated specialist pediatric IF and PSBS center (Table 28.1), that is preferably also close to adult services. Its role is to provide advice, training, and support to local carers, to offer specialist surgical and other clinical services and to generate a reference database and research. The specialist center will cover a wide area and will act as a “hub” offering support to less experienced referring hospitals and local services (“spokes”).


Table 28.1
“Hub and Spoke” model for PSBS care

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Ongoing care is delivered through the local services and the referring hospital, with patients transferring to the center only at the request of local clinicians for specific surgical episodes and planned review. The basic mandate of the central team (Table 28.2) at the hub is to help the parents to manage their child’s problem. The team coordinator and nurse specialists are essential for implementing an agreed patient-specific management plan and for the training and transfer of care to the family and the local carers, thereby retaining a “functional family unit within their local community.”


Table 28.2
Multidisciplinary Team essential to appropriate PSBS management































Team coordinator

The referring hospital

Gastroenterologist

Specialist outreach team

Neonatal-Pediatric Surgeon

HPN team

Psychologist

Social services support

Nutritionist

Family doctor

Pharmacist

Others – radiology, anesthesia

Play workers
 

Transplant team
 


28.4 The Patient-Specific PSBS Management Plan


A high level of cooperation between the different medical specialities and the parents is essential at every stage. Survival is followed by implementation of a patient-specific management plan (Table 28.3) that is agreed between the specialist team at the hub, the local clinical services, and the family. As the child stabilizes, the family rapidly takes on the responsibility for delivery of in-hospital care, including cyclical TPN and enteral feeding, also taking the child home during the daytime. Hospitalization is kept to a minimum, and home parenteral nutrition (HPN) completes the transfer of care to the home.


Table 28.3
Structured plan for management of pediatric short bowel state

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28.5 The “Dedicated” Central Venous Feeding Catheter


A secure central venous catheter is conveniently placed, to be used solely for long-term cyclical parenteral nutrition. The cuffed single-lumen catheter (Broviac), of narrowest gauge consistent with the child’s size and TPN requirement (4.2–6 F), is passed by open or percutaneous access preferably through the neck veins, verifying by intraoperative ultrasound or radiology the tip position at the junction of the superior vena cava with the right atrium. The catheter should be handled only by nominated carers under strict sterile conditions to minimize the risk of infection, occlusion, and central vein thrombosis. Experience has confirmed the much reduced incidence of catheter complications and sepsis associated with nominated catheter care and HPN. At each use the hub should be thoroughly cleansed with a Hibiscrub (Chlorhexidine) soap solution (or similar) and then immersed in absolute alcohol to ensure sterility. After each use it should be flushed with 0.9 % IV saline solution and locked during injection of 1–2 ml of a urokinase solution (1000 units/ml) to avoid intra-catheter backflow and thrombosis and to keep the lumen free of deposits.

It is important to differentiate between catheter-related sepsis with skin organisms (Staphylococcus albus, Staphylococcus aureus) and septicemia from gram-negative intestinal bacteria (Escherichia coli, Klebsiella) that requires appropriate bowel management. Catheter change should be kept to a minimum and only if through-catheter antibiotic therapy and urokinase lock have not been successful at eliminating catheter sepsis. Prolonged broad-spectrum or multiple antibiotic therapy is inadvisable and likely to lead to fungal (Candida) catheter infection, cardiac colonization, and sepsis. Persistent significant infection, irreparable catheter damage, and catheter occlusion will require a change of central line that should be undertaken through the same venous access site as often as possible. Loss of venous access sites for essential TPN seriously compromises long-term survival, limits opportunity for autologous bowel reconstruction, and forces earlier referral for “rescue” bowel transplantation.

Extensive central vein thrombosis is difficult to treat, eventually forcing complex catheter placement transhepatically or by open access to the right atrium. Highly specialist interventional radiological techniques are being developed for canalizing and stenting thrombosed central veins, thereby relieving cardiac strain and establishing the high venous flow that is necessary for a central feeding catheter.


28.6 Total Parenteral Nutrition and Home Parenteral Nutrition


The child with extensive bowel loss and intestinal failure will require a long period of parenteral nutrition to ensure survival and growth. Present-day regimens, although still not perfect, will provide sufficient fluid, electrolytes, and nutrients for normal physical and mental development and for supporting long-term life. Fat- and water-soluble vitamin and trace element supplements (zinc, copper, selenium, manganese) attempt to replace normal intake and reduce deficiencies. It is not the scope of this dissertation to detail the composition of the parenteral solutions and supplements that is available from the manufacturers and appropriate texts. As absorption improves with increasing bowel adaptation, the volume and composition of IV fluid and nutrients and the ratio of parenteral to enteral nutrition will alter with reduction of the parenteral component. It is relevant to track daily calorific intake and to avoid hyperalimentation. Whereas parenteral protein and carbohydrate solutions are now largely standardized, there is still difficulty over the lipid component. Following the work of Clayton [3] and Iyer [4] demonstrating the cholestatic effect of contaminant plant phytosterols, it is now well accepted that plant phytosterols within soya-based lipid solutions induce a rapidly progressive hepatitis and end-stage liver failure. A new less toxic intravenous lipid solution derived from fish oils containing omega-3 fatty acids is preferable for long-term parenteral nutrition; however on its own, it does not provide a full range of essential fatty acids. A combination of small amounts of soya-based lipid, medium-chain triglycerides, olive oil, and fish oil (SMOF) provides a more complete lipid profile.

Once TPN is established and the family is familiar with its cyclical nighttime delivery, appropriate funding and practical arrangements are made for home parenteral nutrition. This is an involved process that requires the provision of sufficient home storage space for equipment and refrigeration facilities for the TPN solutions that are often delivered on a weekly basis by a specialist company. The family home may need spatial adjustment to provide a dedicated “clean area” for central vein catheter care that is so crucial to long-term survival.


28.7 Enteral Nutrition and Brain Learning


Neonatal physiology dictates that the newborn child must learn feeding (bolus formation, swallowing) and food recognition (taste, texture) through the stimulus of normal oral feeding that commences immediately at birth. It is not uncommon in order to maximize absorption that the PSBS child with rapid transit and large enteral losses, is often continuously drip fed by nasogastric or gastrostomy tube and is denied the cyclical oral bolus feeding with normal foods at normal rate and volume that is crucial to brain learning. Food intake and enjoyment is a key element of long-term good quality life, and failure to develop a basic feeding pattern in physiological time will persist as serious “food aversion and denial,” becoming an intractable problem even after enteral autonomy is established.

In striving to maximize absorption, predigested and elemental diets can sometimes prove helpful. However there is little evidence that predigested and elemental diets, even given continuously or cyclically, are better than normal foods at stimulating the mucosal adaptation response and increasing absorption. Additives in the form of starches (rice) and proteins are better absorbed and serve also to thicken the food, whereas fats in the form of medium-chain triglycerides (MCT) are more easily absorbed. It is particularly relevant to remember that food needs to be palatable if it is to be acceptable to the PSBS child, and it cannot be overemphasized that it is normal food given orally and following a normal feeding pattern that are most acceptable and by far the best stimulus for natural mucosal adaptation. It is important to recognize the diverse beneficial effects, in supplementing TPN, of even small amounts of normal foods locally within the bowel and generally following absorption in reducing deficits, protecting the liver and sustaining the intricate enzyme systems relevant to cellular functions.


28.8 Family and Social Life


Long-term survival accentuates the need for a home and social life of quality for both the child and the family. During the initial admission, the delivery of in-hospital care is taken up by the family who learns to set up cyclical parenteral nutrition over the night hours and who takes the child home during the day. HPN allows complete transfer of care to the home and has the advantage of a much reduced rate of central venous feeding catheter sepsis. Home care is supported by local carers and specialist nurses from the “hub” so that the family is kept as a “unit within its local environment” where the child finds opportunity for acceptance and bonding and interaction with siblings and friends.


28.9 Autologous Gastrointestinal Rehabilitation (AGI-R)


The surgical management of the short bowel state is a multistage program working with the natural intestinal adaptation response to increase absorption and to develop new functional bowel suitable for reconstruction [5]. It spans a prolonged period and requires determination and a strong commitment from the patient, the family, and the carers.


28.10 Acute Surgery


Of equal importance to child survival is “bowel salvage” which will determine the quality of long-term life. Thus earlier surgical intervention before bowel necrosis provides an opportunity for minimal resection and maximal conservation of potentially viable bowel. Conventional management with a high proximal jejunostomy on the abdomen or a jejunocolic anastomosis with bowel of similar caliber leads to uncontrollable large volume losses. A large-to-small caliber anastomosis causes “functional obstruction” (Fig. 28.5) with failure of propulsion across a patent anastomosis despite active peristalsis.

It is preferable to establish controllable intraluminal drainage through a tube jejunostomy brought out onto the abdominal wall, with a wide-bore catheter (Malecot, de Pezzer, Foley) that is passed into the distal end of the proximal jejunal loop (Fig. 28.6a, b), also closing off any pre-existing stoma. The child is immediately able to feed orally (Fig. 28.7), providing the crucial natural stimulus for brain learning and a lifelong feeding pattern and delivering the essential nutrient stimulus for mucosal adaptation. A second smaller gauge catheter is passed into the proximal end of any functional distal bowel (commonly the left colon) and brought out onto the abdominal wall. The jejunostomy effluent is stored at 4 °C to limit bacterial overgrowth [6] and is sieved and warmed for recycle through the distal catheter by slow gavage or syringe pump infusion during the night hours, to stimulate adaptation and absorption particularly of fluids and electrolytes from the distal bowel (Fig. 28.8 and Table 28.4).

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Fig. 28.6
Tube jejunostomy: (a) diagram, (b) tube jejunostomy only (no functional bowel distally)


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Fig. 28.7
Tube jejunostomy – child able to feed orally and effluent collected for recycle as in (Fig. 28.8)

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Jul 18, 2017 | Posted by in PEDIATRICS | Comments Off on The Pediatric Short Bowel State: Practical Concepts Toward Enteral Autonomy
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