Ileal Conduit

Anatomy and Physiology

The bladder is an organ that provides a muscular reservoir for the safe storage of urine before its controlled release via the urethra. The bladder is a pelvic organ predominantly comprised of detrusor muscle that can distend to accommodate large volumes of urine. It can contract for extended periods of voiding. 

Urine is created by a complex filtration process within numerous kidney nephrons. Urine then travels from the upper urinary tract, comprising the kidneys and ureters, to the bladder and is expelled from the body through the urethra, which is comprised of the lower urinary tract. An ileal conduit aims to divert urine from the upper urinary tract to a newly formed reservoir created from the terminal ileum. The ureters are disconnected from the bladder and implanted into the conduit. Ureters arise from the renal pelvis and run inferiorly through the abdomen on the surface of the psoas major to cross the pelvic brim at the level of the sacroiliac joints. They continue to cross the bifurcation of the common iliac arteries into the pelvis, where they travel along the pelvic sidewalls until they reach the level of the ischial spines and turn anteromedially towards the bladder. Upon reaching the bladder, they insert obliquely, traveling through the detrusor muscle, which creates a one-way valve that closes on the contraction of the detrusor, thus preventing urine reflux.

The ureters receive their blood supply from various sources depending on their location within the body. For example, the abdominal portion of the ureter receives its blood supply from the renal artery, gonadal artery, and direct branches from the abdominal aorta. The pelvic portion of the ureters gets its blood supply from the superior and inferior vesical arteries.

The ileum is the most distal section of the small bowel and joins the large bowel at the ileocaecal junction, where the ileum and caecum connect via the ileocaecal valve. The ileum comprises 4 layers from the mucosa within the bowel lumen extending outwards through the submucosa, smooth muscle, and the serosa. The ileum receives blood supply, nerve innervation, and lymphatic drainage via mesentery. The ileum's main function is to absorb vitamin B12, bile salts, and other products of digestion. It also has an exocrine function, secreting important enzymes required to break down carbohydrates and proteins, and an endocrine function, secreting hormones such as cholecystokinin into the blood.

During the formation of an ileal conduit, the aim is to change the inherent function of the chosen section of the ileum to provide somewhere to facilitate the passage of urine out of the body. This can cause metabolic problems due to the ileum's highly developed absorptive function. Ammonia and chloride from the urine can be absorbed, causing hyperchloraemic metabolic acidosis.[4]

Indications

Ileal conduits are used to replace the bladder, and as such, the indications for their use involve conditions whereby it is necessary to remove the bladder to improve or prolong a patient's life; for example, neurogenic bladder conditions or severe radiation injury or more commonly where the bladder is harboring a life-limiting pathology such as muscle-invasive bladder cancer T2-T4a, or non-muscle invasive bladder cancer that has failed less radical management such as BCG therapy or recurred after TURBT. An ileal conduit can also be indicated for patients whose bladder symptoms have a severe impact on their quality of life, such as in chronic pelvic pain syndromes or intractable incontinence in females.[5]

Contraindications

A patient's renal function is important when choosing a urinary diversion technique. The ileal conduit is ideal for elderly patients and those with impaired renal function because the bowel segment is short, and there is minimal contact time with urine.[6]  Having prolonged conduit contact time with urine increases the risk of developing metabolic disturbances, particularly metabolic acidosis, due to the absorption from the ileal mucosa of ammonia, hydrogen, and chloride.[7] This results in chronic acidosis and patients are often found to have a respiratory element of compensation on their arterial blood gas. Over time, there is a long-term decrease in renal function regardless of the type of urinary diversion.[8] In the normal population, renal function deteriorates with age; from age 40, the glomerular filtration rate naturally decreases. In patients with ileal conduits, the rate of renal impairment is accelerated by the increased risk of developing repeated urinary tract infections, ureteral obstruction due to stenosis or urolithiasis, and persistent urinary reflux.[7] In patients with chronic renal failure (serum creatinine >1.7 to 2.2 mg/dL), a continent diversion would not be advisable broadly speaking, and a urinary conduit would be offered instead.[6] This differs depending on the operating unit. 

Important patient factors preclude patients from being offered an orthotopic or continent diversion, and these patients should then receive a urinary conduit. These include urethral strictures, a history of inflammatory bowel disease, and pelvic radiation.[6] Patients with pelvic disease at high risk of local recurrence may require radiotherapy and further surgery, which can damage an orthotopic diversion, in which case a urinary conduit should be fashioned instead. Liver disease causing severe hepatic dysfunction is an absolute contraindication to the formation of a continent diversion. 

Relative contraindications to ileal conduit surgery include impaired cognition, which may make learning how to manage a stoma and learning to wake at set times during sleep to empty the bag difficult. Any deficits in manual dexterity are also a relative contraindication, making managing the ileal conduit challenging. 

Equipment

The equipment needed to maintain the stoma can be categorized into intraoperatively and postoperatively. The operative technique section of this review covers the equipment used. The long-term management of the stoma requires stoma bags and anti-adhesive spray. Occasionally, stoma paste, stoma rings, and barrier cream are also needed, particularly in the case of an ileal conduit, as urine can cause excoriation of the skin.

Personnel

To perform this operation safely, it is essential to have a full theatre team, including a surgical team, an anesthetic team, operating department practitioners (ODPs), a scrub team, and recovery nurses for post-operative care. These patients often require ITU care, and their involvement beforehand can be vital. Sometimes, depending on co-morbidities, patients may also need to go to a high-risk anesthetic clinic pre-operatively to optimize them for theatre.

Another key component of a patient's preparation for surgery involves interaction with the stoma nurses to provide patients with information to prepare themselves mentally for the life-changing event of having a stoma. They also provide support and aftercare for patients with ileal conduits and are often the first point of contact for those living with an ileal conduit.

Preparation

Preparation for surgery is key in subsequent patient outcomes. There are multiple components to preparing someone for an ileal conduit, arising first from the initial consultation involving their diagnosis and further discussing the operative procedure itself and what creating an ileal conduit involves. They may need to be referred to other multidisciplinary team members to optimize their cardiovascular status via focussed anesthetic assessment and exercise programs. The patient also needs to be prepared for both the practicalities and psychological impact of living with a stoma.

The stoma site should be chosen with care and often after the patient has worn an appliance filled with water and tested lying down, sitting up, and with and without clothes on. The operating surgeon should ensure that the stoma is not placed on a scar, skin crease, or under the beltline. The stoma nurses' early input in the patient journey is key so patients know what to expect after their surgery, which helps them progress quickly with their recovery.

Technique or Treatment

There are variations in the approach to forming an ileal conduit; however, the main principles of the operation are described here. It can be performed open via a laparotomy, laparoscopically or robotically assisted:

The first stage isolates the ileal loop; approximately a 15 cm ileal segment is identified 15 cm from the ileocaecal junction.[9] This segment of the ileum is then inspected for its suitability as a conduit; for example, there is no evidence of inflammatory bowel disease. Next, it is important to ensure that the identified ileum reaches the stoma site tension-free before dividing it and that the vascular arcade within the mesentery is not disturbed. In obese patients, the length of the ileum needs to be longer to avoid tension on the stoma. The mesentery to the selected ileal segment must be divided with care to preserve the blood supply to both the conduit and the ileo-ileal anastomosis; a Kelly clamp and ties or an energy device can be used. When dividing the bowel, it is important to mark the distal end that forms the stoma. A GIA stapler or non-crushing clamps and scalpel can divide the bowel. The remaining 2 ends of the ileum are anastomosed using a stapled or hand-sewn technique to restore bowel continuity, and the mesenteric window is closed with vicryl sutures. Upon completing the anastomosis, the ileal segment for the conduit should be below that of the ileal anastomosis.

The second stage involves mobilizing the ureters. This should be performed from the lateral side of the ureters as much as possible to preserve their blood supply. The distal ends of the ureters should be handled as little as possible to avoid traumatizing the tissue required for the anastomosis. The left ureter is moved to the right side of the abdomen through a window created in the mesentery behind the sigmoid colon. It is important that the blood supply to the sigmoid colon is not compromised and that the window is wide enough to avoid any constriction or tension on the left ureter. The distal ends of the ureters can be cut and sent for analysis to see if there is an extension of cancer, and that would

The third stage is the ureteroenteric anastomosis; this can be an end-to-side anastomosis (Bricker technique) where the 2 ureters are anastomosed to the proximal end of the conduit at slightly different locations to avoid any compromise in blood supply. A full-thickness enterotomy is created on the side of the conduit; the ureter is spatulated and then anastomosed to the conduit, taking interrupted full-thickness bites of both the ureter and bowel using 4.0 or 5.0 PDS.[6] A ureteric stent can be placed across the anastomosis and securely fixed to the conduit.

The Wallace technique is another popular ureteroenteric anastomosis that requires the proximal end of the conduit to be left open initially and then closed with the 2 ureters anastomosed over the end. The ureters are spatulated and laid adjacent to each other to be stitched together using PDS; both apexes are aligned together, and the distal ends of the ureters are combined. The free edges of the ureters are then anastomosed to the open end of the conduit, sealing it off.

One potential downside to the Wallace technique is that a recurrence in 1 ureter may compromise the other ureter. No matter which technique is used, several surgical principles apply to both, including maintaining an adequate distal ureteral blood supply, a tension-free anastomosis, and avoiding ureteral kinking or twisting.

The fourth stage is creating the stoma via a trephine incision, where a circular piece of skin is removed at the pre-marked stoma site, followed by dissection down to the anterior rectus sheath, where a cruciate incision is made. Below the anterior sheath, the rectus muscles are split, and then entry into the peritoneal cavity is gained. The gap in the fascia should be able to admit 2 fingers. Once this has occurred, the distal end of the conduit is delivered through to the skin using a Babcock, ensuring there is no twist in the conduit. The stoma is then matured and spouted to prevent skin excoriation around the stoma site.

Complications

Urinary conduits are often considered easier to perform than continent diversions as the surgical technique is less complicated and requires less time. An ileal conduit does not require anastomosis to the urethra; it also requires a shorter bowel segment to create the conduit. The conduit itself requires minimal augmentation when compared to a neobladder.[6]  Most of the complications of ileal conduits can be split into early (<90 days) and late (>90 days).[10][11]

Early complications include those involving the bowel, such as obstruction, anastomotic leak, and ileus. Ileus can occur in up to 20% of cases and is often the reason for prolonged hospital admission. The urinary leak is also important and accounts for about 7% of complications.[12] This often occurs due to tension at the anastomosis 

Delayed complications include those involving the newly formed stoma, such as parastomal hernia, retraction or stenosis, and bleeding. Frequent urinary tract infections (UTIs) can often be a problem for patients, and up to 6% end up dying from end-stage renal failure. These patients are also predisposed to developing renal stones; ultrasound (USS) imaging can detect this. Metabolic complications can be significant; hence, regular follow-up is needed to ensure electrolytes are normal and the patient is not acidotic. Patients can struggle with the psychological impact of living with a stoma and should be appropriately counseled beforehand.

Clinical Significance

Resection of a part of the subterminal ileum for constructing an ileal conduit can lead to patients developing vitamin B12 deficiency. This is because the terminal ileum is the predominant site of micronutrients such as B12 and magnesium absorption.[6] This is not usually seen for a few years post-operatively as the body has a large reserve of vitamin B12. This increases a patient's risk of macrocytic or megaloblastic anemia and subacute combined degeneration of the spinal cord. Levels should be checked at follow-up appointments every 6-12 months.[13] It is taught to avoid using large terminal ileum segments to reduce the risk of this complication. This is especially important in patients with an ileal disease such as Crohn's disease.[6]

Another complication is metabolic hyperchloraemic acidosis, which can occur in up to 15% of patients, especially in those patients with impaired renal function.[4] These patients require regular blood tests to detect metabolic abnormalities up to 15 years postoperatively, as they are at risk of osteoporosis.

Enhancing Healthcare Team Outcomes

Despite the numerous papers in the literature, there is conflicting evidence and no clear advantage in the quality of life of orthoptic diversions over incontinent diversions.[6]  Psychosocial factors are an important consideration for patients undergoing this surgery. Up to two-thirds of patients with an ileal conduit require help from their spouse or another caretaker to take care of their appliance and urostomy. Still, with an aging population, many older people live alone with no one to help take care of them.[14] 

Due to stoma-related skin excoriation, stoma care is critical to prevent complications and associated decreases in quality of life. The journey from diagnosis through treatment and subsequent follow-up is challenging, and a support system is vital for successful patient outcomes. Preoperative counseling and shared decision-making are vital, with each individual's social factors taken into consideration, as they can drastically influence treatment plans.[6]