Differentials
Lumbar spondylosis/disc herniation
SIGNS / SYMPTOMS
Pain is relieved by sitting.
Pain and/or tenderness may involve the sacrum or lumbar spine, without specific tenderness of the coccyx.
No pain or tenderness on palpation of the coccyx, or on rectal examination.
INVESTIGATIONS
Injection of corticosteroid around the dorsal surface of the coccyx does not relieve pain, indicating pain is referred.
MRI of the lumbosacral spine may reveal the site of degenerative disc disease or disc herniation.
Proctalgia fugax
SIGNS / SYMPTOMS
Episodic sudden, severe pain in the anal canal that lasts only seconds or minutes. May awaken the patient from sleep.[9]
No coccygeal tenderness or pain on rectal examination.[9]
INVESTIGATIONS
Dynamic lateral sacrococcygeal x-ray may be normal and shows neither sacrococcygeal hypermobility (>20° on sitting) nor subluxation.
Levator ani syndrome
SIGNS / SYMPTOMS
Also known as puborectal syndrome, levator spasm, or pelvic floor myalgia.
This category may include some cases of idiopathic coccygodynia.[22]
Dull ache or pressure sensation in the rectum, exacerbated by prolonged sitting or supine position, which may last hours to days.
Tenderness of puborectalis muscle on rectal examination.[9]
INVESTIGATIONS
Anorectal manometry may show increased pressure; however, this test is controversial.
Although some studies have shown increased anal canal pressure and correlated pain relief with a decrease in pressure, other authors have discouraged its routine use, citing unreliability in its diagnostic and predictive value.[9]
Alcock's canal syndrome
SIGNS / SYMPTOMS
Also known as pudendal canal syndrome or pudendal nerve entrapment.
Unilateral or bilateral burning, prickling, stabbing, or numbness in the perineum, external genitalia, or scrotum.
Pain is worse with sitting and there is a sense of a foreign object in the urethra, rectum, or vagina.[9]
INVESTIGATIONS
Diagnosis is essentially clinical.
MRI reveals normal anatomy; intercurrent disease unrelated to the diagnosis; or, occasionally, a nerve sheath tumour.
Pudendal nerve motor latency studies (nerve conduction studies) are usually normal, as sensory fibres are affected preferentially.
Diagnostic nerve block, consisting of anaesthetic infiltration within the pudendal canal, results in pain relief for the duration of anaesthesia, but may be technique dependent.[23]
Descending perineum syndrome
SIGNS / SYMPTOMS
Incomplete emptying of stool as the rectal wall mucosa prolapses into the anal canal, followed by dull aching in the perineum and rectum.
The anus may protrude with straining.
Weak pelvic floor on rectal examination.[24]
INVESTIGATIONS
Digital rectal examination reveals weak pelvic floor and lack of coccygeal tenderness. Inspection reveals the anus descending below the level of the coccyx.
Piriformis syndrome
SIGNS / SYMPTOMS
Buttock pain radiating down the posterior thigh that may be worse with sitting, exercise, and bending at the waist.
Can be provoked by internal rotation of the flexed thigh (Freiberg's manoeuvre).
May coexist with coccygodynia.[17]
INVESTIGATIONS
MRI rules out lumbosacral pathology as evidenced by degenerative disc disease and/or disc herniation, or, less commonly, tumour or perineural (Tarlov) cyst.
Magnetic resonance neurography may reveal increased signal in the proximal sciatic nerve.[25]
Anogenital syndrome
SIGNS / SYMPTOMS
A descriptive diagnosis involving irritating and painful symptoms in the genitourinary, perineal, and anal areas.
Perineal or prostatic pain with suprapubic pain and tenderness is present.
Irritation of the anal sphincter inhibits voiding.
INVESTIGATIONS
Diagnosis is clinical and based on the history and physical examination. Digital rectal examination may reveal exquisite prostatic tenderness.
Perianal abscess and/or fistula
SIGNS / SYMPTOMS
A perianal abscess may present with erythema, a sensation of fullness, or a fluctuant mass on digital rectal examination. Fever, chills, and perianal pain are present.
A fistula presents as a small opening adjacent to the anus.
INVESTIGATIONS
Contrast-enhanced CT or MRI of the sacrum and pelvis reveals an abscess cavity and/or fistula tract.
WBC count, CRP, and erythrocyte sedimentation rate may be elevated.
Rectal tumours or teratomas
SIGNS / SYMPTOMS
A rare cause of coccygodynia.
May present with blood or mucus in the stool, painful defecation, diarrhoea, or straining.
Direct extension to the sacrum and coccyx may cause local pain and tenderness.
Digital rectal examination reveals a mass.
Teratomas are seen in younger age groups.
INVESTIGATIONS
Contrast-enhanced CT or MRI reveals a mass in the retrorectal space or pelvic cavity, with or without involvement of the sacrum and coccyx.
Perineural (Tarlov) cyst
SIGNS / SYMPTOMS
A rare cause of coccygodynia.[12][13]
Sacral perineural cysts may rarely present with coccygeal pain.
May be accompanied by urinary disturbance and pain in the groin region.
INVESTIGATIONS
MRI of the sacrum reveals nerve root cysts of cerebrospinal fluid signal intensity (bright on T2-weighted sequences).
CT may reveal enlargement of the sacral foramina or thinning of the sacral lamina around the cyst.
A perineural (Tarlov) cyst might fill on contrast myelography.
No relief of pain on coccygeal injection with corticosteroid.
Pilonidal cyst
SIGNS / SYMPTOMS
A pilonidal cyst develops along the dorsal surface of the coccyx near the gluteal fold.
Usually contains hair and debris.
There may be localised pain, erythema, or drainage of pus from a sinus tract.
May be caused by excessive sitting.
Direct trauma can result in cyst inflammation and exacerbation of symptoms.
Typically affects young men aged 15 to 24 years.
INVESTIGATIONS
Diagnosis is based on history and examination.
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