Atonic/Hypotonic Bladder
Basic Information 
Synonym(s)
Atonic or paralytic bladder, lower motor neuron bladder, spastic bladder, upper motor neuron bladder
Clinical Presentation
Disease Forms/Subtypes
• Upper motor neuron or spastic bladder: Lack of descending inhibition, turgid bladder, increased urethral sphincter tone, periodic uncontrolled high-pressure urine production, and incomplete bladder emptying. The bladder is difficult to express by transrectal compression. The urethra is difficult to catheterize because of increased tone.
• Lower motor neuron or paralytic bladder: Loss of sensory fibers signaling bladder wall stretching that normally initiates urination. Detrusor muscle innervation and contractility are lost. The bladder fills to capacity and then passively overflows. The bladder is easily compressed per rectum, allowing urine voiding.
• Automatic bladder: Spinal cord damage cranial to the sacrum. Bladder filling and uncontrolled reflex emptying caused by loss of upper motor neuron influence. Higher sensation of bladder fill is lost, and emptying is incomplete.
Physical Exam Findings
• Urine scalding over the perineum and between the hind legs.
• Frequent attempts to urinate or uncontrolled voiding.
• Perineal analgesia, loss of tail tone, loss of anal tone, fecal incontinence.
• Abnormalities of pelvic limb gait and regional muscle wasting may occur.
• Signs referable to more widespread neurologic dysfunction may be present.
Etiology and Pathophysiology
• Sympathetic, parasympathetic, and somatic branches of the central nervous system are required to coordinate bladder function.
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