Symptomatic hyperphosphataemia following phosphate enema in a healthy adult.

Editor,

Adequate colonic cleansing is essential for accurate and safe colonic procedures1. Common preparations for cleansing include diet in combination with a cathartic agent (stimulants), gut lavage, and phosphate preparations (osmotics). Phosphate preparations offer an attractive alternative due to smaller volumes required for ingestion. We report an unusual case of acute hyperphosphataemia following the administration of a phosphate enema.

Case report

A 79 year lady with a six month history of lower abdominal cramps and diarrhoea including mucous per rectum underwent flexible sigmoidoscopy. She had taken one sachet of picolax (10mg sodium picosulfate) as bowel preparation the night before and reported minimal effect. As such she received a single phosphate enema at 09.30. This contained 30.8g of sodium phosphate in 118ml delivered by a standard rectal tube. She became unwell within 10-15 minutes with severe nausea and dizziness. Observations demonstrated a heart rate of 86 beats per minute and a blood pressure of 80/34mmHg. Bloods were taken for urea and electrolytes and a normal saline infusion was started. Over the subsequent 90 minutes her blood pressure improved to a systolic of 100mmHg and her heart rate fell to 60 beats per minute. Her blood results were normal with the exception of a phosphate of 2.65 mmol/L (0.8 – 1.55). Her symptoms and clinical observations continued to improve and by 11.30 she was able to undergo flexible sigmoidoscopy which was normal. Repeat blood tests two days later were normal (phosphate 1.31mmol/L). At subsequent outpatient review a small bowel series and ultrasound scan of abdomen were normal. Barium enema demonstrated mild sigmoid diverticular disease. Eight months later her gastro-intestinal symptoms had settled.

Discussion

Asymptomatic hyperphosphataemia with levels 2-3 times above normal has been reported in nearly 25% of individuals with normal renal function after administration of oral phosphate-based laxatives2. Current recommendations3 simply suggest caution in the elderly and those with renal impairment. Multiple case reports exist warning of the dangers of oral phosphate-based laxatives in patients with renal disease and in paediatrics and only a handful of accounts of hyperphosphataemia have been reported in patients receiving phosphate-based enemas in similar patient groups4,5.

The mechanism of hyperphosphataemia in renal impairment is felt to be secondary to decreased excretion of phosphate by the kidneys. In paediatrics it is believed to occur due to large volumes of phosphate containing solution, relative to the child's size. Other recognised causes following oral phosphate based laxatives include Hirschsprung's disease, faecal impaction, or functional intestinal obstruction where increased gastrointestinal phosphate absorption may occur, elderly age because of the diminished intestinal motility, and increased intestinal permeability in the presence of inflammatory intestinal disorders6.

There are no cases in the literature of hyperphosphataemia arising due to diverticular disease following phosphate-based enema. However one could postulate that, for the reasons mentioned above, it could be an aetiological factor albeit unlikely in this instance due to the absence of significant disease or active inflammation. In summary this case report highlights the need for vigilance even in patients deemed low risk of developing hyperphosphataemia following a phosphate-based enema.