Renal stone formation in space

Renal stone formation and passage during space flight can potentially pose a severe risk to crew member health and safety and could affect mission outcome.

[2] Cystine stones, caused by hereditary cystinuria, begin forming in childhood and can grow large enough to fill the renal collection system.

[6] Oral alkali (such as potassium citrate) raises the urine's pH and helps suppress calcium oxalate crystal formation.

[8] Potassium citrate has also been shown to reduce bone loss in postmenopausal women[9] and also improves calcium balance in patients with distal renal tubular acidosis[10] Bed rest studies[11] are used as ground-based analogs to space flight environments.

[12] The Integrated Medical Model (IMM)[13] group at Glenn Research Center in Ohio has been analyzing and optimizing data gathered on renal stone formation since late 2008.

Since the risk of renal stone formation could, as has,[clarification needed] result in the loss of a crew member to a mission,[1] regular testing is conducted.

To date, there has been only one inflight instance of renal stone formation (described in detail in Valentin Lebedev's book, Diary of a Cosmonaut: Two hundred eleven days in space).

[15] Data gathered during 129- to 208-day Shuttle-Mir missions suggest that the spaceflight environment and subsequent return to Earth change the composition of the astronauts' urine and promoted the formation of renal stones.

The aim of this experiment was to evaluate the in-flight effectiveness of potassium citrate as a countermeasure against the formation of renal stones during long duration space flight.

Unidentified kidney stone.
This micrograph shows calcium oxalate crystals in urine. These small crystals can develop to form renal stones. The Renal Stone Risk During Space Flight experiment is conducted aboard the International Space Station.
Spiked rods of uric acid crystals from a synovial fluid sample, photographed under polarized light.
Struvite (magnesium ammonium phosphate) stones removed from a dog's urinary bladder.
Figure 4-1. Calcium balance during and after Skylab missions. Adapted from Rambaut and Johnston (1979) [ 14 ]
Figure 4-2a. Representative preflight renal stone risk profile determined in a single crew member before a short-duration flight (i.e., Space Shuttle). BLUE bars represent decreased risk, RED bars represent increased risk.
Figure 4-2b. Representative postflight renal stone risk profile determined in the same crewmember immediately following a short-duration flight (i.e., Space Shuttle). Blue bars represent decreased risk, red bars represent increased risk.