Keywords
Currarino triad - presacral cyst - anorectal malformation - MRI
New Insights and the Importance for the Pediatric Surgeon
Currarino triad is a rare syndrome that may be occasionally encountered during managing
cases of anorectal anomalies. Increased awareness of this rare condition can help
in achieving early detection, allowing for a more effective way of management.
Introduction
Currarino triad is a rare congenital disorder characterized by the presence of three
components: anorectal anomaly, sacral vertebral defect, and a presacral mass (lipomyelomeningocele
and/or developmental cyst).[1]
[2] Cases may present with the complete form of the triad or may lack one of the three
components.[3] Unlike other forms of sacral agenesis, Currarino triad is characterized by partial
dysplasia sparing the first sacral vertebra.[1]
[4] The characteristic sacral defect (sacral scimitar) is considered the key for making
the diagnosis.[5]
Early reports in the literature were described by Kennedy[6] and Ashcraft and Holder.[7] However, the triad was named after an American radiologist “Guido Currarino,” who
was the first to describe the triad as a unique syndrome with characteristic genetic
inheritance and provided embryological explanation for its occurrence.[1] Increased awareness of this rare condition can help in achieving early detection,
allowing for a more effective way of management.
Case Presentation
A male patient presented at birth with anorectal malformation ([Fig. 1A]); there were no signs of meconium staining in the urine or the perineum. A divided
pelvic colostomy with distal mucous fistula was performed. Echocardiogram and abdominal
ultrasound were negative for possible associated cardiac and renal anomalies.
Fig. 1 (A) A 3-month-old boy with anorectal anomaly underwent colostomy at birth. (B,C) The contrast study “distal colostogram” performed in anteroposterior and lateral
views showing blind rectal termination with no evidence of fistulous communication
with the urinary tract (imperforate anus without fistula). Note: a radio-opaque mark
has been placed indicating the site of anal dimple on the perineum (arrow). (D) Anteroposterior view of the plain X-ray showing the characteristic sacral defect
(sacral scimitar). Note: the sacral notch cannot be detected in the lateral view of
sacrum (C) and has been masked by the contrast in the anteroposterior view (B).
At the age of 3 months, a high-pressure distal colostogram was performed as a preparatory
step for a PSARP (posterior sagittal anorectoplasty) procedure.[8] The distal colostogram demonstrated a blind rectal termination with no evidence
of fistulous communication with the urinary tract (imperforate anus without fistula;
[Fig. 1B, C]).
At the time of operation, the mother revealed that her elder daughter (now 6 years
old) underwent a similar operation. Revising the medical records of her daughter revealed
a case of Currarino triad: anal stenosis (funnel anus), vertebral defect, and presacral
cyst. Because of the reported autosomal dominant inheritance in cases of Currarino
triad,[1]
[9] we suspected that this boy might have a similar pathology. Reexamination of his
X-ray studies revealed a missed sacral notch in the plain X-ray ([Fig. 1D]) in addition to widening of the retrorectal space in lateral contrast film ([Fig. 1C]). The diagnosis of familial Currarino triad was quite evident in this boy (like
his sister). A decision had to be made whether to postpone the operation and wait
for a preoperative pelvic magnetic resonance imaging (MRI) study (for better delineation
of the anatomy) or to proceed with the PSARP procedure and explore the presacral space
during operation. Influenced by the busy operative schedule and the author's previous
surgical experience with similar cases,[5] we decided to operate.
With the patient in the prone position, a generous posterior sagittal incision was
made for mobilization of the anorectum and exploration of the presacral space. We
started as usual by dissection of the fascia around the posterior and the lateral
aspects of the rectal pouch. A small midline incision was made in the posterior wall
of the rectum to inspect for any missed communication with the urinary tract and to
guide the dissection during separation of the anterior rectal wall from the intimately
adherent urinary tract. After mobilization of the anorectum, a retrorectal cyst (∼2 cm
in diameter) was found and excised. Then, the steps of anorectoplasty were completed
as usual by reconstruction of the levator ani and striated muscle complex around the
neorectum.
Postoperative recovery was uneventful. Histopathological examination of excised specimen
revealed fibromuscular tissue showing multiple clefts lined by stratified squamous
epithelium and entrapped transitional epithelial islands. These histopathological
findings go with the diagnosis of a developmental cyst associating with Currarino
triad.[10]
[11]
[12]
Later, a postoperative pelvic MRI was ordered that revealed residual presacral cystic
lesion ([Fig. 2A, B]), with the absence of spinal cord anomalies. The patient was scheduled for reoperation
to excise the residual presacral mass while still having a diverting colostomy. This
time, the patient was positioned in the supine (lithotomy) position, which provided
better exposure to the presacral space. Initially, the lesion was obscured by its
deep location and surrounding fat; however, deeper dissection directed toward the
bony defect (sacral notch) enabled successful identification and excision of the lesion
([Fig. 2C]). Although the preoperative MRI did not identify any communication between the lesion
and the thecal sac, yet careful closure of the bed of the excised lesion was followed.
Again, we had uneventful postoperative recovery and histopathological analysis of
the excised specimen returned similar to the previous one. Six weeks later, the patient
underwent colostomy closure.
Fig. 2 Follow-up magnetic resonance imaging (MRI) study performed after posterior sagittal
anorectoplasty showing a residual presacral mass (*) in midsagittal T2-weighted image
(A) and axial T2-weighted image (B). (C) Reoperation in the supine lithotomy position to remove the residual presacral mass
(*); note: the incision is posterior to the neoanus (white arrow).
The patient was seen at follow-up 3 months after the closure of colostomy. He defecates
spontaneously once every 1 to 2 days. He is still only 19 months old and therefore
below the age of voluntary bowel control. However, the mother was informed about the
possibility of constipation, problems with fecal continence, and the need for long-term
follow-up. The mother has had a similar experience with her elder daughter who is
now 6 years old and has voluntary bowel and urinary control. The parents (being the
first-degree relatives of our case) were advised to perform screening by plain X-ray
sacrum.
Discussion
Currarino triad is a rare syndrome that may be occasionally encountered during managing
cases of anorectal anomalies. The triad consists of anorectal anomaly, sacral bony
defect, and a presacral mass.[1] It has a reported female predominance and genetic inheritance. Identification of
the characteristic notched sacrum (sacral scimitar) in plain X-ray (anteroposterior
view) is considered the key for the diagnosis; however, not infrequently, this radiological
sign is overlooked, especially with a small sacral defect and a constipated child.[5] Increased awareness about this condition among neonatologists and pediatric surgeons
can help in early picking of affected cases and better planning of surgical treatment.
Currarino triad is caused by heterozygous mutation in the MNX1 (previously HLXB9) gene on chromosome 7q36. The disorder is an autosomal dominant genetic trait that
has variable expressivity.[9] Mutations in the coding sequence of the MNX1 gene have been identified in nearly all cases of familial Currarino's syndrome and
in approximately 30% of patients with sporadic Currarino's syndrome.[13] Lynch et al. reported that 4% of patients with a mutation in the gene were asymptomatic
and had normal sacral X-ray imaging.[14] Cytogenetic analysis of a previously reported family with Currarino triad showed
that the mother of the two affected children carried a balanced translocation between
chromosome 7q36 and 12q24. Both children were monosomic for 7q36, as they had inherited
the deleted chromosome 7 from their mother.[15]
All affected families should be offered genetic counseling, as awareness of the hereditary
nature of the disorder allows identification of asymptomatic heterozygotes and patients
at risk, which leads to better planning of pregnancies and appropriate management
of affected patients. All first-degree relatives of patients with Currarino triad
should be screened by pelvic X-ray due to a highly variable phenotype within most families.[9] Relatives with an abnormal X-ray should be referred to a surgeon for further investigations, including pelvic MRI
for an occult presacral mass due to significant inter- and intrafamilial variability
in expression.[9]
[14]
The presacral mass in Currarino triad may be a lipoma, lipomyelomeningocele, or some
sort of developmental cyst.[1]
[2]
[5] The latter has been frequently described in the literature as a mature cystic teratoma,
which has been considered by Weinberg to be a misnomer in cases of Currarino triad.[12] There are several observations concerning the presacral cysts associating with Currarino
triad that would support the diagnosis of a developmental cyst rather than a true
neoplasm (teratoma).[11] It is usually recommended to excise presacral developmental cysts as these are liable
for infection and abscess formation.[5] On the other hand, presacral lipomas and meningoceles can be managed conservatively
unless symptomatic.[5] Large lesions may cause obstructive symptoms (constipation) and may distort the
surgical field during the repair of anorectal anomaly in addition to other related
obstetric considerations.[5]
Excision of the presacral cyst is usually performed concomitantly during anorectoplasty.
The prone position is the standard approach for PSARP in males;[8] however, in females, the supine position can be used as an alternative (anterior
sagittal anorectoplasty).[16] In this case report, excision of the presacral cyst took place in two steps: the
first excision during the PSARP procedure in the prone position, and a second operation
in the supine lithotomy position to remove a residual component of the lesion that
was missed during the primary operation. It was clear that the supine lithotomy position
provided better access to explore the presacral space than the prone position, especially
with a deeply located cyst as in our case. Other lessons learned from managing this
case were the importance of proper history taking in surgical practice, possible association
of Currarino triad with different types of Anorectal anomalies (not necessarily the
“funnel” anus or rectoperineal anomalies), and, lastly, the necessity of performing
preoperative MRI to complete the diagnosis in cases of anorectal anomalies associated
with sacral defects, which might have spared our case a second operation.
There was some delay initially in completing the diagnosis for this case; however,
the management was completed with a satisfactory outcome. Lastly, the prognosis for
continence may be generally good for this case owing to the absence of associated
spinal cord anomalies.[5]
