Фосфатная нефропатия: причины, диагностика и лечение осложнений после подготовки к колоноскопии.

Phosphate nephropathy or nephrocalcinosis is an adverse renal condition that arises with a formation of phosphate crystals within the kidney's tubules. This renal insufficiency is associated with the use of oral sodium phosphate (OSP) such as C. B. Fleet's Phospho soda and Salix's Visocol, for bowel cleansing prior to a colonoscopy. the measure of creatinine level, GFR level, and urine output, urine microscopy, and urinalysis. Different management approaches involve the use of alternative bowel preparation agents and increasing patients' risk assessment among healthcare professionals, including nephrologists, gastroenterologists, and renal pathologists. Other agents used for bowel preparation (e. g. magnesium citrate or PEG 3350 & electrolyte based purgatives such as Colyte or Golytely) do not carry this risk. TOC

Patients with phosphate nephropathy have variable outcomes, either being recognised as developing acute kidney injury, the abrupt loss in renal failure, or being undiagnosed. For example, events including diarrhea, vomiting, dehydration, sepsis, and hypotension following the colonoscopy, can indicate the risk of phosphate nephropathy and raise the concern for acute tubular necrosis. Significant electrolyte abnormalities including hypocalcemia, hypernatremia, and hypomagnesemia are also the outcomes of the use of OSP. The elevated phosphorus load, or hyperphosphatemia, can reduce the phosphorus reabsorption in the kidney’s proximal tubular within minutes of OSP ingestion.

Phosphate nephropathy can be diagnosed via different types of assessment, most of which are also used to detect acute kidney injury and chronic kidney disease. The more than 1.5 fold increase in serum creatinine level, or the more than 25% decrease in GFR, or the decrease in urine output less than 0.5mL/kg/h within 6 hours, signify the risk of attaining acute kidney injury after ingestion of OPS. Via examining the urinary sediments, calcium phosphate crystals are identified, and the associated phosphate nephropathy is determined. In addition, there are other relevant bowel preparation agents that can be used in line with the colonoscopy guidelines including electrolyte based purgatives such as Golytely, Polyethylene glycol (PEG), sodium picosulfate, and sodium laxatives. These bowel preparation alternatives show the same efficacy with OSP and cause less frequently and significantly side effects and complications than OSP.

Upon the early detection, phosphate nephropathy can be treated with a timely renal replacement therapy such as haemodialysis or peritoneal dialysis in order to decelerate the calcium phosphate crystallization process. Haemodialysis is performed to assist the renal excretion via removing accumulated toxins, especially the overproduction of reactive oxygen species at the damaged tubular epithelial cells. The complete recovery of renal function after phosphate nephropathy progression to acute kidney injury or to chronic kidney disease, was reported to be rare.

Mannitol and large volume of saline were first used as bowel preparation agents prior to colonoscopy. As the use of Mannitol causes the production of methane, hydrogen, and other flammable gases, it was reported to be associated with colonic explosion. Large volume of saline was also reported to significantly impact the electrolyte balance and net fluid within the body. Later in the 1990, the polyethylene glycol electrolyte lavage solution or PEG ELS, was formulated with more effectiveness and safety to use. PEG ELS was not widely adopted due to its requirement of consuming an enormous volume. Then, OSP (C. B. Fleet's Phospho soda) in the form of tablets with the same efficacy as PEG ELS, was chosen as a safe alternative bowel preparation agent. Later, in 1975, acute kidney injury and potential chronic kidney disease were first found to be related to the ingestion of OSP. Then, in 2003, an adverse incident of calcium phosphate deposition within the renal tubules was first reported following the use of OSP. This was linked to the tubular injury and other renal complications as well as the emergence of the term “phosphate nephropathy”.