Overview
Definition:
A retrorectal (or tailgut) cyst is a rare, congenital or acquired benign cystic lesion located in the presacral space posterior to the rectum and anterior to the sacrum and coccyx
It arises from vestigial remnants of the embryonic tailgut, a developmental structure that normally regresses by the 8th week of gestation
These cysts can vary in size and may contain mucoid, serous, or sebaceous material
They are often asymptomatic but can present with symptoms due to mass effect or complications.
Epidemiology:
Retrorectal cysts are uncommon, with an estimated incidence of 1 in 40,000 to 1 in 50,000 live births
They are more frequently diagnosed in adults, with a female predilection
Most cases are diagnosed incidentally or when symptomatic
Congenital origin is considered the most common, with sporadic occurrence.
Clinical Significance:
While benign, retrorectal cysts can lead to significant morbidity if left undiagnosed or untreated
They can cause local compression symptoms affecting bowel, bladder, or sciatic nerve function
Complications such as infection, hemorrhage, malignant transformation (though extremely rare), and fistulae necessitate surgical intervention
Accurate diagnosis and timely excision are crucial for symptom relief and preventing complications, making this a relevant topic for surgical residents preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Asymptomatic presentation is common, discovered incidentally on imaging
When symptomatic, patients may report a palpable mass in the gluteal or sacrococcygeal region
Pelvic or perineal pain, often exacerbated by defecation or prolonged sitting
Constipation or changes in bowel habits due to rectal compression
Urinary symptoms such as frequency, urgency, or hesitancy due to bladder compression
Sciatic pain or neurological deficits if the cyst impinges on sacral nerves
Perianal discomfort or discharge if a fistula develops.
Signs:
A palpable mass may be present in the sacrococcygeal area or on digital rectal examination, typically located posteriorly
Tenderness over the sacrococcygeal region
Signs of infection (erythema, warmth, purulent discharge) if the cyst is abscessed
Neurological deficits (e.g., weakness, sensory loss in the distribution of sacral nerves) are uncommon but possible.
Diagnostic Criteria:
There are no specific diagnostic criteria universally established for retrorectal cysts
Diagnosis is primarily based on a combination of clinical suspicion, characteristic findings on imaging modalities, and exclusion of other presacral masses
Histopathological examination of the excised specimen confirms the diagnosis.
Diagnostic Approach
History Taking:
Detailed history focusing on the duration and progression of symptoms
Characterization of pain (location, aggravating/relieving factors)
Bowel and bladder function
Any history of previous surgery or trauma to the region
Family history of congenital anomalies or tumors
Red flags: rapid growth of a mass, signs of infection, neurological deficits, or suspicion of malignancy.
Physical Examination:
Comprehensive physical examination including abdominal palpation for masses
Thorough digital rectal examination to assess for a posterior mass, its size, consistency, mobility, and relationship to the rectal wall
Examination of the gluteal and sacrococcygeal regions for external abnormalities or a palpable mass
Neurological assessment of the lower extremities and perianal sensation.
Investigations:
Magnetic Resonance Imaging (MRI) of the pelvis and sacrococcygeal region is the investigation of choice, providing excellent detail of cystic contents, relationship to adjacent structures, and identifying potential complications
Computed Tomography (CT) scan can also be useful for characterizing calcifications and bony involvement but has lower soft tissue resolution than MRI
Ultrasound may be used as an initial screening tool or in pediatric patients
Plain radiographs of the sacrum and coccyx can assess for bony abnormalities but are less useful for soft tissue evaluation
Biopsy is generally not recommended pre-operatively due to the risk of infection and seeding, unless malignancy is strongly suspected.
Differential Diagnosis:
Other presacral masses including teratomas, dermoid cysts, epidermoid cysts, enterogenous cysts, meningoceles, schwannomas, neurofibromas, chordomas, sarcomas, abscesses (e.g., post-traumatic, post-surgical, or related to inflammatory bowel disease), and lymphangiomas
Differentiating features: MRI findings (cystic vs
solid components, internal septations, signal characteristics) are crucial
Congenital anomalies are often associated with other spinal or sacral abnormalities.
Management
Initial Management:
For asymptomatic cysts, observation with regular follow-up imaging may be considered, especially in young patients with small lesions
However, given the potential for complications and growth, surgical excision is often recommended even for asymptomatic cysts, particularly in adults.
Medical Management:
Medical management is typically not indicated for retrorectal cysts themselves
Antibiotics may be used to treat associated infections or abscesses
Pain management with analgesics can be provided for symptomatic relief.
Surgical Management:
Surgical excision is the definitive treatment
The approach depends on the cyst's size, location, and relationship to surrounding structures
Options include: Posterior (sacrococcygeal) approach: This is the most common approach, allowing direct access to the presacral space
It is suitable for most cysts, especially those located inferior to the S3 vertebra
The dissection is performed carefully to avoid injury to the rectum, sacral nerves, and coccyx
Anterior approach: Rarely used, typically for very large cysts extending anteriorly or in conjunction with other procedures
Transanal approach: Limited to very small cysts that are anteriorly located and easily accessible via the rectal lumen, often performed with endoscopic assistance
Laparoscopic or robotic approaches: May be considered for larger or higher-lying cysts to facilitate dissection and minimize surgical trauma, but require specialized expertise.
Supportive Care:
Preoperative bowel preparation is essential
Postoperatively, patients require pain management, monitoring for wound complications, and management of bowel/bladder function
Adequate hydration and early mobilization are encouraged
Stool softeners may be prescribed to reduce straining.
Complications
Early Complications:
Hemorrhage during or after surgery
Infection of the surgical site or cyst cavity
Rectal injury or perforation
Injury to sacral nerves leading to motor or sensory deficits
Wound dehiscence
Retained cyst fragments leading to recurrence or infection.
Late Complications:
Recurrence of the cyst due to incomplete excision or regeneration from residual tissue
Chronic pain or neurological symptoms
Development of a fistula
Malignant transformation (very rare but a reported complication).
Prevention Strategies:
Meticulous surgical technique with careful dissection to ensure complete cyst excision and preservation of vital structures
Intraoperative neuromonitoring can help identify and prevent nerve injury
Aggressive management of any intraoperative bleeding
Prophylactic antibiotics to reduce surgical site infection
Careful wound closure and drainage if necessary.
Prognosis
Factors Affecting Prognosis:
Complete excision is key to good prognosis
The presence of infection or significant neurological involvement at presentation may affect functional recovery
The rarity of malignant transformation means that the prognosis for benign cysts is generally excellent following complete surgical removal.
Outcomes:
With successful surgical excision, symptomatic relief is usually achieved, and the risk of recurrence is minimized
Patients generally return to normal activity levels
Long-term functional outcomes are favorable, provided there is no significant pre-existing nerve damage or complications from surgery.
Follow Up:
Postoperative follow-up typically includes clinical examination and, depending on the complexity of the case and surgeon preference, imaging (e.g., MRI) at 6-12 months to rule out recurrence
Long-term follow-up may be considered for patients with extensive or complex cysts, or in cases where complete resection was uncertain.
Key Points
Exam Focus:
Retrorectal (tailgut) cysts are rare presacral cysts of congenital origin
MRI is the gold standard for diagnosis
Surgical excision is the definitive treatment
Differential diagnosis includes a wide range of benign and malignant presacral masses
Potential complications include infection, nerve injury, and recurrence
Complete excision is paramount for good outcomes.
Clinical Pearls:
Always consider a retrorectal cyst in the differential diagnosis of a posterior pelvic mass or unexplained sacrococcygeal/perineal pain
Digital rectal examination is a crucial part of the physical assessment
Be extra vigilant during dissection to protect sacral nerves and the rectal wall
Thorough histopathological examination of the specimen is mandatory to confirm the diagnosis and rule out malignancy.
Common Mistakes:
Misdiagnosing a retrorectal cyst as a perianal abscess or other common anal pathologies
Incomplete excision leading to recurrence
Premature biopsy of a suspected cyst, risking infection
Failure to obtain adequate imaging (MRI) to fully assess the cyst and its relationship to surrounding structures
Inadequate surgical planning based on insufficient preoperative assessment.