Cloacal Malformations

Etiology

The etiology of these conditions remains unknown.

Epidemiology

The incidence of cloacal anomalies is estimated to be 1 per 50000 live births, although many cloacal malformations may be misdiagnosed as a rectovaginal fistula.[2] Thus the actual incidence may be higher. They are seen exclusively in females.

Pathophysiology

Cloacal malformations result from failure of the embryonic anorectal and urogenital channels to separate during the sixth and seventh gestational weeks.[3] The current belief is that earlier arrest of normal embryologic processes results in a longer common channel which has reconstructive and functional implications later in life.

History and Physical

Prenatal diagnosis is uncommon in patients with a cloaca, although prenatal ultrasound or MRI may identify a cystic pelvic structure in the pelvis of a female patient consistent with a fluid-filled vagina (hydrocolpos).[2]  Additional prenatal orthopedic or renal findings make the diagnosis of cloaca more likely.

The definitive diagnosis of cloacal malformation is made in the newborn period by physical examination with the identification of a single perineal orifice, usually posterior to the clitoris. A thorough perineal examination with adequate lighting is required, which is best accomplished by retracting the labia “up and out” to assess the relation of the urethra to the hymen. In cloacal malformations, the urethra is inside the hymen, or the anterior hymen is absent. If the urethra is distal to the hymen, then a cloaca can be ruled out. Further examination of the genitalia may demonstrate a diminutive and foreshortened labia minora and a clitoral hood. Abdominal examination may divulge the presence of a mass in the lower abdomen which likely represents a hydrocolpos which can be present in as many of 40% of patients with a cloaca.[1]

Evaluation

Initial evaluation of a patient with a cloacal malformation involves the identification and treatment of any associated life-threatening anomalies. Like other ARMs, cloacas often correlate with various anomalies in the vertebral, anorectal, cardiac, tracheoesophageal fistula, renal, and limb (VACTERL) association.[4] Early consultation with a pediatric urologist or a pediatric surgeon with experience in cloacal management is necessary upon confirmed diagnosis.

A thorough urologic assessment is mandatory in the newborn period.[5] Structural and functional urologic anomalies, including hydronephrosis, renal agenesis, renal dysplasia, horseshoe kidney, are common in patients with cloaca and are found in up to 90% of cases.[1][6][7] Urologic and renal dysfunction account for significant long-term morbidity in patients with the cloaca, and early identification of anomalies and appropriate intervention can optimize long-term renal health.

Identification of spinal anomalies is necessary as there is a high association of cloaca and tethered cord.[8] This analysis can be performed using ultrasound within the first 3 months of age, or an MRI after 3 months due to ossification of the sacrum and coccyx. The decision to de-tether a cord is a clinical one based on imaging and function effects of diagnosed with the help of urodynamics. The indications for de-tethering vary in each institution. There appear to be clear urologic benefits, although the impact on fecal continence has not been clearly shown.

An assessment of the sacrum can be performed with anteroposterior (AP) and lateral sacral x-rays to assess for sacral anomalies and determine the sacral ratio.[9] The sacral ratio is the length of the sacrum from the sacroiliac joint to the tip of the coccyx over the distance of the iliac crest to the sacroiliac joint. Dedicated lateral sacral x-rays are necessary for this calculation as films in the anterior-posterior plane can be affected by the tilt of the pelvis, yielding an inaccurate calculation. This ratio serves as a marker of development of the pelvic musculature and nerves essential to bowel and bladder function later in life and can form the basis for counseling families on their child’s functional prognosis. AP images are useful for identifying hemivertebrae or other sacral anomalies.

Treatment / Management

Initial Management

After stabilizing the child, the initial goal is to identify and drain a hydrocolpos, if present.[1] A hydrocolpos is a fluid-filled vagina that compresses the bladder anteriorly at the trigone where the ureters enter, causing hydroureternephrosis and obstructive uropathy. This condition is best investigated with an ultrasound of the abdomen and pelvis. Drainage can be performed by catheterizing the common channel; however, it is necessary to confirm that the hydrocolpos has undergone adequate emptying as the catheter may enter the bladder or a single hemivagina resulting in the drainage of fluid but not adequate decompression of the hydrocolpos. Catheterization, therefore, may not a reliable long-term strategy in all patients and definitive drainage with a vaginostomy should be a consideration in those patients with recurrent or inadequate drainage to ensure proper decompression of the urinary system. Rarely, if the bladder does not adequately empty despite adequate treatment of the hydrocolpos, urinary diversion can be performed at the time of colostomy creation with a vesicostomy or placement of a suprapubic cystostomy tube.[1](B2)

Early surgical management aims to divert the fecal stream with a descending colostomy with mucous fistula creation. Consideration should be given to the placement of the colostomy and length of the distal segment as this portion of the bowel will be used for the future pull through. A loop colostomy is not recommended as the distal limb remains in continuity with the urinary tract; thus any spillage of stool risks contamination of the urinary system and urinary tract infection.

Treatment Planning 

Definitive surgical repair requires the identification and measurement of several pelvic structures, including:

• Length of the common channel
• Length of the urethra
• The presence and length of a vagina
• The presence of a hemivagina or longitudinal vaginal septum
• The presence of a cervix (or multiple cervices)
• Visualization of the height of the rectum and location of the rectal fistula relative to the pubococcygeal (PC) line.

The length of the common channel and urethra are critical for surgical planning (e.g., to decide whether to perform a urogenital separation or total urogenital mobilization). The 3 cm common channel is traditionally taught as the cutoff between simple and complex cloacas.[10] The presence and length of the patient’s native vagina are necessary to determine the likelihood of needing to perform a vaginal replacement at the time of PSARVUP. Additional details of the gynecologic anatomy are necessary as any necessary gynecologic procedures (e.g., vaginal septum excision) can be performed simultaneously. This information is also essential for long-term gynecologic counseling. Precise knowledge of the location of the rectum is necessary to correctly identify whether it is reachable from a posterior sagittal approach or if laparoscopy or laparotomy will be needed. This decision will have a significant effect on the anesthetic plan as well as the postoperative care of the patient.

No standardized imaging protocols exist at present, but endoscopy and 3D cloacagram are two useful modalities to assess the patient’s anatomy.[11] Some authors have suggested that the role of MRI will probably become more important in the future.[12](B2)

Definitive Treatment

The definitive management of cloaca is surgical, with the goal of separating the gastrointestinal, gynecologic, and urologic structures and creating a perineal opening for each of the three structures for optimization of the function of each system, and to create a catheterizable urethra.[1][13][14](B2)

The surgical management of this condition has evolved significantly over the last several decades. In 1982, Pena first described the posterior sagittal approach for the repair of a cloacal malformation; an operation termed the posterior sagittal anorectovaginourethroplasty (PSARVUP).[15] The technique described separating the vagina from the common channel using a technique called a urogenital separation. The fine dissection in the plane between the vagina and urethra often resulted in devascularization of the tissue resulting in urethrovaginal fistulae, which can be a very debilitating complication of urogenital separation.

In 1997, the total urogenital mobilization (TUM) was described as a technique to mobilize the vagina and urethra as a single unit, thereby obviating the need to mobilize the tissue between these two structures.[16] This procedure, however, risks leaving the patient with a urethra which is too short and a bladder neck which is below the urogenital diaphragm, resulting in urinary incontinence.[17] Wood, therefore, proposed an algorithm in 2016 which considers both the length of the common channel and native urethra to leave the patient with a urethra of adequate length to maximize urinary continence.[10]

Definitive repair is typically performed between 6 and 12 months of age. The specific details of the repair are beyond the scope of this manuscript; it is performed through a posterior sagittal incision, with the addition of a laparoscopic or open approach to mobilize a high rectum or vagina as dictated by the patient’s anatomy.

Differential Diagnosis

The differential diagnosis of cloaca includes less severe ARM subtypes (e.g., rectovaginal fistula, rectovestibular fistula, imperforate anus with no fistula) with or without vaginal atresia. These diagnoses can be ruled out based on a thorough physical examination.

Treatment Planning

As stated above, definitive surgical repair requires the identification and measurement of several pelvic structures, including:

• Length of the common channel
• Length of the urethra
• Presence and length of a vagina
• Presence of a hemivagina or longitudinal vaginal septum
• The presence of a cervix (or multiple cervices)
• Visualization of the height of the rectum and location of the rectal fistula

The length of the common channel and urethra are critical for surgical planning (e.g., to decide whether to perform a urogenital separation or total urogenital mobilization). The 3 cm common channel is traditionally taught as the cutoff between simple and complex cloacas. The presence and length of the patient’s native vagina are necessary to determine the likelihood of needing to perform a vaginal replacement at the time of PSARVUP. Additional details of the gynecologic anatomy are necessary as any necessary gynecologic procedures (e.g., vaginal septum excision) can be performed simultaneously. This information is also necessary for long-term gynecologic counseling. Precise knowledge of the location of the rectum is necessary to correctly identify whether it is reachable from a posterior sagittal approach or if laparoscopy or laparotomy will be needed. This decision will have a significant effect on the anesthetic plan as well as the postoperative care of the patient.

No standardized imaging protocols exist at present, but endoscopy and 3D cloacagram are two useful modalities to assess the patient’s anatomy.

Prognosis

Urinary and bowel continence in patients with cloacal malformations are related primarily to the length of the common channel and the presence of other anomalies, in particular, the degree of sacral development and the presence of tethered spinal cord. Patients with a common channel of greater than 3 cm, tethered cord, and a sacral ratio of less than 0.4 tend to have worse functional outcomes.[18] However, these spinal and sacral anomalies are more commonly present in patients with more complex cloacal malformations, and a complete understanding of the individual contribution of the spine and sacrum to these functional outcomes remains unknown in patients with cloaca. Some patients with poor colorectal and urologic function may require bowel and bladder reconstruction later in childhood which can be performed simultaneously.[19]

Complications

Inability to correctly diagnose a cloaca in the newborn period may fail to identify obstructing uropathy caused by a hydrocolpos which may cause sepsis, acidosis, and in severe cases renal failure. With misdiagnosis of the cloaca in the newborn period, the surgeon may only repair the rectal component of the malformation and leave a persistent urogenital sinus. The most concerning postoperative complication is the development of a urethrovaginal fistula which requires surgical repair if proximal to the urinary sphincter.