Kidney stones are a common medical challenge, with unique considerations during pregnancy. Managing them requires balancing the well-being of both the pregnant person and the developing fetus.
Understanding Kidney Stones in Pregnancy
Kidney stones are solid deposits of minerals and salts that form within the kidneys. Pregnancy brings physiological changes that influence stone formation. Increased progesterone can cause ureters to relax and dilate, slowing urine flow and leading to urinary stasis. This physiological hydronephrosis, or kidney swelling from urine buildup, occurs in many pregnant individuals, sometimes as early as six weeks gestation.
Urine composition also changes during pregnancy, promoting stone formation. Increased renal plasma flow and glomerular filtration rate lead to higher excretion of substances like calcium, uric acid, sodium, and oxalate. While stone inhibitors like citrate and magnesium also increase, altered urine chemistry and a higher urine pH can shift stone type, making calcium phosphate stones more prevalent in pregnant individuals than calcium oxalate stones.
Recognizing Symptoms and Safe Diagnosis
Symptoms of kidney stones in pregnancy resemble those in the general population but can be hard to distinguish from common pregnancy discomforts. Individuals may experience sharp pain in the side, back, or lower abdomen, often radiating to the groin and occurring in waves. Nausea, vomiting, increased urinary urgency or frequency, painful urination, and blood in the urine (hematuria) are common indicators. Fever or chills may develop if an infection is present.
Given the overlap with other pregnancy issues like preterm labor or urinary tract infections, prompt medical evaluation is important. Diagnostic methods prioritize the safety of both the pregnant person and the fetus. Urinalysis is an initial test for blood, infection, or crystals in the urine. Blood tests assess kidney function and detect factors like elevated calcium levels.
Ultrasound is the preferred imaging method for diagnosing kidney stones during pregnancy due to its lack of radiation exposure. It effectively detects stones and assesses for urinary obstruction. While computed tomography (CT) scans are accurate, they are generally avoided during pregnancy due to radiation, unless absolutely necessary. Magnetic resonance imaging (MRI) is another radiation-free option.
Treatment Approaches During Pregnancy
The primary goals of kidney stone treatment during pregnancy are to manage pain, facilitate stone passage, and prevent complications, prioritizing maternal and fetal well-being. Initial management often involves conservative approaches, as many stones, particularly those up to 4mm, pass spontaneously. This includes adequate hydration to dilute urine and promote stone movement. Pain relief uses analgesics safe for pregnancy, such as acetaminophen; NSAIDs are generally avoided due to fetal risks.
If conservative measures are insufficient or complications like infection or persistent obstruction arise, interventional procedures may be necessary. Ureteral stents are thin, flexible tubes placed in the ureter to bypass a stone and allow urine to drain. These temporary stents may require periodic changes due to increased encrustation risk during pregnancy. Percutaneous nephrostomy tubes offer another option for draining urine directly from the kidney if a stent is not feasible.
Ureteroscopy, which involves inserting a small telescope through the urethra and bladder into the ureter to visualize and remove or break up stones, is a safe and effective treatment for pregnant individuals not responding to conservative management. This procedure can often be performed with minimal fluoroscopy and sometimes under local anesthesia or light sedation to minimize fetal exposure. In contrast, extracorporeal shock wave lithotripsy (ESWL), which uses shock waves to break stones, is contraindicated during pregnancy due to potential adverse fetal effects. Percutaneous nephrolithotomy (PCNL), a more invasive surgical procedure, is postponed until after delivery due to anesthesia and radiation risks.
Preventive Measures
Reducing the risk of kidney stone formation during pregnancy involves several lifestyle modifications. Adequate hydration is a primary preventive measure; pregnant individuals should drink enough fluids, mainly water, to ensure their urine remains diluted and light in color. This prevents the concentration of stone-forming substances.
Dietary adjustments also play a role in prevention. These include:
- Limiting sodium intake, as high sodium can increase calcium excretion in urine.
- Maintaining a balanced calcium intake, preferably from dietary sources like dairy, rather than excessive supplementation.
- Reducing oxalate-rich foods such as spinach, beets, and chocolate for individuals prone to calcium oxalate stones.
- Limiting purine-rich foods like red meat and seafood for those susceptible to uric acid stones.
Regular prenatal care is important, allowing healthcare providers to monitor kidney function and urine composition, enabling early detection of abnormalities that could contribute to stone formation.