A Christmas tree has been used to describe the appearance of a flaccid (hypotonic) neurogenic bladder, in which the volume is large, pressure is low, and contractions are absent.

A Christmas tree or pine cone bladder will present when a bladder is elongated and pointed with a thickened (trabeculated) wall. It is typically seen in severe neurogenic bladder caused by neurologic damage. Symptoms can include overflow incontinence, frequency, urgency, urge incontinence, and retention.

Consultant urologist, Dr Jeremy Thomas said neurogenic bladders are common, but the Christmas tree image often seen in X-rays isn’t. Dr Thomas said these findings are not specific characteristics or symptoms of a neurogenic bladder and can be seen in patients with lesions anywhere along the sacral reflex arc leading to poor detrusor compliance.

The detrusor muscle is located within the walls of the bladder and it impacts urination. The detrusor muscle is essentially what most people refer to as the bladder. The detrusor muscle relaxes to allow urine to fill the bladder and stretches to hold more urine. When it is time to urinate, the detrusor muscle contracts to push urine out of the bladder.

Occasionally, Dr Thomas said, poor detrusor compliance is also seen in bladder neck obstruction of a non-neurogenic cause.

Regarding the ‘Christmas tree’ bladder, Dr Thomas said it is essentially the shape a bladder can take when the ‘wiring’ to it has gone all wrong or doesn’t function in sync.

In addition, he said it usually occurs where there is disruption of the micturition reflex, which can occur at any level in the central nervous system from medulla to lumbar spine.

The micturition reflex, according to Dr Thomas, is the sphincter at the bladder neck relaxing or opening when the bladder contracts to allow urine out, but with this ‘neurogenic bladder’, the coordinating signals via the nerves and spinal cord are lost.

Further, the consultant urologist said repetitive contraction of the bladder against a sphincter that is closed will lead to high and dangerous pressures within the bladder, similar to a muscle hypertrophying with repeated heavyweight lifting.

Hypertrophying refers to the cells of an organ increasing in size in adapting to the increased workload.

Dr Thomas said the hypertrophying can present elevated pressures to the kidneys and result in irreversible damage if not treated early.