Keywords
posterior cloaca - urorectal malformation sequence - aphallia
Introduction
A posterior cloaca is defined as a urogenital sinus which diverges posteriorly and
terminates in the anterior rectal wall.[1] When the urogenital sinus opens anterior to a normally placed anus, it is considered
a posterior cloaca variant ([Fig. 1]).[1] The description of this rare anorectal malformation is highly variable in terms
of the anatomy of the external genitalia, number of perineal orifices, and aberrant
Müllerian structures, with associated renal and cardiac defects.[1] We present three cases with similar unusual external genitalia, anorectal malformation,
and renal insufficiency ([Table 1]). Reconstruction in the surviving patient involved transperineal total urogenital
mobilization and introitoplasty, sparing the anal canal.
Table 1
Summary of the perineal anatomy and associated anomalies of the patients
|
Case 1
|
Case 2
|
Case 3
|
|
- Fused labioscrotal folds
- No corporal tissue
- No palpable gonads
→ Two perineal orifices
|
- Fused labioscrotal folds
- No corporal tissue
- No palpable gonads
→ Single perineal orifice
|
- Fused labioscrotal folds
- No corporal tissue
- No palpable gonads
→ Two perineal orifices
|
|
Hydrocolpos
Two hemivaginas
|
Hydrocolpos
Bicornuate uterus
|
Hydrocolpos
|
|
Bilateral hydronephrosis
|
Bilateral hydronephrosis
|
Solitary left kidney
Accessory urethra
|
|
______
|
Distended bladder
|
Distended floppy bladder
|
|
Atrial septal defect
|
Patent ductus arteriosus
|
______
|
|
______
|
Deficient abdominal muscles
|
Deficient abdominal muscles
|
Fig. 1 Midline fused labioscrotal folds forming an anterior sac devoid of corpora.
Case 1
A term neonate born at 2,975 g was referred on day 3 of life. On arrival she was clinically
stable and passing urine and stool via two closely situated perineal orifices, separated
by a common wall. The posterior orifice was partially surrounded by sphincters. Anterior
to these orifices was a large midline sac devoid of corpora and gonads, consistent
with large fused labioscrotal folds ([Figs. 1] and [2]). There was no catherizable channel within this structure. Urgent surgical intervention
included a midline laparotomy, with a vaginostomy, drainage of bilateral hydrocolpos
with division of vaginal septum, and a divided colostomy. On postoperative day 3,
she required a relook laparotomy for abdominal wall dehiscence, during which a suprapubic
catheter was placed for bladder decompression. Imaging of the urinary system demonstrated
bilateral hydronephrosis with mild hydronephrosis on the right and moderate on the
left. The urinary bladder was noted to be collapsed and there was no evidence of residual
hydrocolpos. Despite these interventions, the patient succumbed to renal failure a
few days later.
Fig. 2 Perineal view demonstrating two orifices with the posterior orifice (anus) partially
or fully within sphincters.
Case 2
A term neonate with prenatal diagnoses of bilateral hydronephrosis, anhydramnios,
and pulmonary hypoplasia was delivered at our center. The parents had declined second-trimester
termination of pregnancy, and no antenatal chromosomal analysis was performed. At
birth the child was found to have deficient abdominal wall musculature, bilateral
clubfeet, ambiguous genitalia with a midline fluid-filled sac in place of a clitoris,
and a single perineal orifice ([Fig. 1]). A plain radiograph demonstrated a poorly developed sacrum. At laparotomy, hydrocolpos
of a single vagina, a bicornate uterus, and a markedly distended bladder were documented.
She underwent diversion with a divided colostomy, vaginostomy, and vesicostomy. Intra-
and postoperatively, the patient had persistent severe metabolic acidosis and was
anuric which led to a fatal outcome.
Case 3
A term baby girl was referred at 3 weeks of age with ambiguous genitalia and an anorectal
malformation. Antenatal ultrasound at 35 weeks had revealed hydronephrosis of a solitary
left kidney and a single umbilical artery. Postnatal chromosomal analysis confirmed
a 46 XX karyotype. Post-delivery she was well and not requiring any organ support.
The child was feeding and passing stool and urine. On examination, she had a mildly
distended abdomen and a palpable left kidney. Her perineal examination included a
hyperpigmented anterior sac with rugae which was fluid filled and located between
the labia majora. Posterior to the sac were two perineal openings: an anterior opening
draining urine and a posterior, normally sited anus surrounded by well-developed sphincters
(see [Figs. 1] and [2]). A plain radiograph demonstrated a normal sacrum.
She underwent examination under anesthesia and laparotomy. At laparotomy, she underwent
a vaginostomy for hydrocolpos of a non-septated vagina, a vesicostomy for a distended
bladder, and an end colostomy. A divided colostomy was deemed unnecessary, given the
clearly patent and appropriately located anus. Postoperative recovery was uneventful.
The diagnostic workup for associated congenital anomalies included a renal ultrasound,
which demonstrated resolving hydronephrosis of her single left kidney and a structurally
normal heart on echocardiogram.
At the age of 7 months, she underwent cystovaginoscopy and contrast studies for surgical
planning. Our center offers two-dimensional fluoroscopy, which was used to plan the
reconstruction. Pertinent findings included a thick pubic bone and an anus within
sphincters that calibrated to a Hegar 14 with a normal dentate line. An accessory
urethra was suspected due to urine drainage from the sac but was not initially identified.
A transperineal total urogenital mobilization (TUM) was performed with the patient
in supine position. Stay sutures were placed around the urogenital sinus and circumferential
incision was made to begin mobilization. The incision was extended anteriorly though
the midline of the sac. During mobilization of the urogenital sinus the orthotopic
urethra was identified and catheterized. On opening the sac structure, accessory rudimentary
urethra was seen. The proximal extent was unclear, and it was ligated and excised.
Despite the presence of pubic symphysis hypertrophy, there was no need to resect any
cartilage or bony elements to create space for the mobilization. Genitoplasty was
achieved by midline division and folding of the labioscrotal sac around the TUM forming
labia minora around the introitus. The anus was left untouched. The vaginostomy tube
was removed. Urine was diverted via the vesicostomy and a transurethral catheter for
1 month postoperatively ([Fig. 3]). The cosmetic outcome was satisfactory (see [Fig. 4]), and postoperative cystovaginoscopy confirmed a normal urethral length and one
patent vaginal orifice. At 18 months old she underwent closure of her colostomy. Her
continence outcomes are yet to be assessed as she is not yet toilet trained.
Fig. 3 Case 3: Intraoperative photos. Left to right in supine position with anterior sagittal
incision. (A) Urogenital sinus held by two sutures, Foley catheter in orthotopic urethra and red
vessel loop around dorsal atretic accessory urethra. (B) Introitoplasty: Labioscrotal sac opened, and two halves fashioned into labia minora.
(C) Final result with preserved native anus, perineal body created, and visible urethral
and vaginal openings at perineum.
Fig. 4 Case 3: 1 month post reconstruction with good cosmetic outcome.
Discussion and Conclusion
In the original 1998 description of posterior cloaca, Peña and Kessler described both
types of posterior cloaca, noting that the posterior cloaca variant (two orifices)
may be more accurately classified as a variant of the urogenital sinus rather than
a true cloacal malformation.[2]
[Fig. 5] However, because both types of posterior cloaca share features and associated abnormalities
typical of cloaca patients, the authors recommended including them within the broader
spectrum of cloacal malformations.[1]
[2] Furthermore, in 2010, Peña et al proposed that the posterior cloaca in females and
aphallia in males may represent parts of the same spectrum, given the phenotypic similarities.[1] In both patient groups, there is typically a prominently developed pubic bone, a
posteriorly displaced urogenital sinus, and a spectrum of hypoplastic orthotopic urethra,
ranging from complete absence to varying degrees of urethral stenosis. These conditions
have been collectively referred to by some authors as “partial uro-rectal septal defects.”[3]
Fig. 5 Schematic representation of posterior cloaca types.
In cases with a single perineal orifice, the main differential diagnosis are: typical
cloacal malformation, where the orifice opens at the level of the urethra or just
above it; classic posterior cloaca, where the orifice opens in the position of a normally
located anus; and penile agenesis, which can phenotypically resemble posterior cloaca
but is usually distinguishable by the presence of palpable gonads within the scrotum.[4] When two perineal orifices are present, the principal alternative diagnosis is the
classical urogenital sinus, where the opening is located more anteriorly than in the
posterior cloaca variant, typically in the position of a normal urethra, and which
may be associated with other disorders of sexual development.[1]
[2]
Since clinical examination generally allows reliable distinction of posterior cloaca
from both penile agenesis and urogenital sinus, and assessment of the internal anatomy,
including the gonads and Müllerian structures, can be performed at the time of diversion,
we do not consider karyotype analysis mandatory in patients with posterior cloaca.
In keeping with the literature, hydrocolpos was found in all three cases with two
of them also exhibiting additional Müllerian anomalies. Of interest, none of the three
cases had significant structural cardiac and renal anomalies, and although renal dysfunction
was a critical factor in the fatal outcomes, it occurred in the absence of major anatomical
urological abnormalities. This observation supports the notion that renal insufficiency
can result from functional rather than structural pathology, as previously described.
The terminology used to describe these variants is variable, contributing to uncertainty
around the true incidence of posterior cloaca. Other terms used to describe the same
defect include partial urorectal septal defect.[1] Cloacal malformations are considered by some to form part of the urorectal septum
malformation sequence (URMS).[5] There are a few unique features common to our three cases that are in support of
the association with the URMS, namely, the genital fold anomaly which lack corporal
structures (effectively aphallia or absent penis),[1] the anteriorly displaced anal canal, and echogenic kidneys. The renal findings effectively
demonstrate that there can be renal insufficiency without an anatomical urological
abnormality.[2]
[5] Additional findings supportive of the URMS spectrum found in Case 2 include deficient
abdominal wall musculature, sacral anomaly, and limb abnormalities; and in Case 3
include a single umbilical artery, solitary kidney, duplicated Y-shaped urethra, and
pubic bone thickening.[5]
Although the pathogenesis of the posterior cloaca remains debated, its clinical implication
is clear. Management requires prenatal counseling where possible, comprehensive diagnostic
evaluation, timely organ support, and a staged surgical approach.[6] The final goals of treatment in posterior cloaca are the same as other cloacal malformations:
preservation of renal function, achievement of social continence, and satisfactory
genital reconstruction.[6]
[7]
Fecal stream diversion is usually described as a divided sigmoid colostomy; however,
end-colostomy in the case of an adequate size perineal fistula is acceptable.[8] Urinary tract decompression may be facilitated by vaginostomy alone or may require
an additional vesicostomy.[7] In our series, a large, atonic bladder that was difficult to catheterize was a common
finding, and vesicostomy proved useful in facilitating bladder drainage and potentially
preserving already compromised renal function. When assessing the Müllerian structures
at initial surgery, vaginal septi must be taken down to adequately drain hydrocolpos
in the case of hemivaginas.[1]
Later in childhood, definitive reconstruction is guided by detailed imaging and endoscopy.
Panendoscopy with catheter placement facilitates a cloacagram, and surgeon's presence
during two-dimensional fluoroscopy can improve interpretation of overlapping structures.[8] However, even with endoscopy and cloacagram, accurately identifying and delineating
urethral anomalies can be difficult despite strong clinical suspicion, as seen in
our experience.
Reconstruction in classic posterior cloaca may be achieved with a sagittal trans-anorectal
approach.[2] In posterior cloaca variants, where the anus is normally positioned within a functioning
sphincter complex, it should be preserved to avoid muscle and nerve injury,[9] with only a total urogenital mobilization (TUM) being performed.[1] This allows the blood supply to the urethra and vagina to be left intact.[6] A rudimentary dorsal atretic urethra is a common finding in posterior cloacas, and
it may be resected in the case of a good caliber functioning orthotopic urethra.[1]
[6] The thick pubic bone and cartilage hypertrophy may require carving to allow space
for reconstruction.[9] External genital reconstruction depends on the available skin and presence of corporal
structures or accessory urethrae. A feminizing genitoplasty has been described by
splitting the end of the urogenital sinus to form labia minora.[6] In our third case, we describe a novel approach for genital reconstruction combined
with the TUM. Using the fused labioscrotal folds we created labia minora around the
vaginal introitus. This technique also allowed to achieve a visible urethral meatus,
while preserving urethral length, which can be used to perform clean intermittent
catheterization.[1] However, normal continence of stool and urine is expected in these patients, except
in the case of sacral dysplasia.[6] In survivors, medium-term follow-up should focus on continence outcomes, while long-term
care must consider menstrual and sexual health.[6]
In conclusion, posterior cloaca variants are rare and complex anorectal malformations
often associated with renal insufficiency. The phenotype described here, characterized
by a midline labioscrotal sac, appears linked to poor renal outcomes. In survivors,
individualized surgical planning, including total urogenital mobilization and reconstruction
using the labioscrotal folds, can yield promising cosmetic results. This series expands
the known spectrum of posterior cloaca and introduces a novel approach to genitoplasty.
Long-term functional outcomes remain to be evaluated.
