Pregnancy and Urolithiasis Treatment & Management
- Author: Robert O Wayment, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS more...
The initial management of urolithiasis in pregnancy should be conservative. Intravenous hydration and analgesia have been shown to result in spontaneous passage of symptomatic calculi in 64-84% of patients.[6, 7] Bed rest, antiemetics, and antibiotics are also important, when indicated.
Some stones may simply become asymptomatic, allowing delay of further treatment. Symptomatic urolithiasis is more likely to resolve when calculi are located in the renal pelvis as opposed to the distal ureter.
Treatment goals in the remaining patients are to reduce maternal discomfort, to prevent renal damage and sepsis due to obstructing calculi, and to minimize risks to the fetus. If conservative measures fail to relieve clinical symptoms or to pass calculi, appropriate surgical intervention should be undertaken.
Urine should be strained to obtain stones when they are passed. Chemical analysis should then be performed to guide postpartum treatment and diet modifications to prevent future stone formation. However, because of the physiologic and electrolytic changes associated with pregnancy, metabolic studies should be postponed until completion of pregnancy.
Several narcotics have been tested for use during pregnancy. Morphine sulfate, hydromorphone, butorphanol, meperidine, and acetaminophen provide temporary symptomatic relief without harming the fetus. However, avoid codeine during pregnancy because of its association with fetal defects. Long-term use of narcotics in pregnancy can lead to fetal narcotic addiction and even intrauterine growth retardation (IUGR) or premature labor. 
Nonsteroidal anti-inflammatory drugs (NSAIDs) are also contraindicated because of an increased risk of miscarriage when used in the first trimester. In addition, fetal renal anomalies, fetal pulmonary hypertension, and premature closure of the ductus arteriosus are risks when NSAIDS are prescribed close to term.
Medical expulsive therapy (MET): Ureteral stone passage may be facilitated by alpha-adrenoceptor blockers. These agents promote relaxation of ureteral smooth muscle and have been found to increase rates of stone passage, to hasten stone passage, and to decrease the amount of pain associated with stone passage. [32, 33] Although these studies have not addressed the use of alpha-adrenoceptor blockers in pregnant women, the authors have successfully used alpha-blockade as MET therapy in several pregnant patients with ureterolithiasis in conjunction with the attending obstetrician. The authors recommend that consultation with the attending obstetrician is recommended before this therapy is instituted.
Calcium stone disease
Medical management for reduction of calcium stone disease is contraindicated. Thiazide diuretics, which markedly reduce calciuria and resultant stone formation, are a viable treatment option for urolithiasis in the general population. However, thiazide diuretics are contraindicated during pregnancy because they may induce fetal thrombocytopenia, hypoglycemia, and hyponatremia. Additionally, diuretics are generally dangerous because they may interfere with the normal extracellular volume expansion of pregnancy.
The safest method of medically managing calcium stone disease during pregnancy is to increase fluid intake and to avoid excessive calcium intake (including calcium-fortified prenatal vitamins). Typically, calcium intake should not exceed 1000-1200 mg/d during pregnancy. This treatment may prevent or reduce the risk of urolithiasis during pregnancy. Sodium intake and protein consumption should also be curtailed.
Uric acid disease
In uric acid stone disease, xanthine oxidase inhibitors (eg, allopurinol) prevent uric acid stone formation by inhibiting the final step in human purine metabolism, thereby decreasing both serum and urinary uric acid levels. However, use of xanthine oxidase inhibitors is contraindicated during pregnancy because the effects of the drug on the fetus are unknown. Alternative treatment modalities for uric acid stones during pregnancy include increasing fluid intake, limiting dietary purine intake, and increasing urinary alkalinization.
Cystine stone disease
Patients with cystine stone disease often have known cystinuria prior to conception. Despite contraindications to the use of common drug therapy, research has shown that careful medical management can allow women with cystinuria who form stones to safely undergo pregnancy without increased risk.
Penicillamine reduces cystine stone formation by interchanging disulfide bonds with cystine residues, thereby separating cystine-cystine bonds and allowing increased cystine solubility. Severe or serious adverse effects occur in about 50% of patients. Because penicillamine has been reported to cause fetal abnormalities in rats, it is contraindicated during pregnancy.
Increasing urinary volume to 3000 mL and urine alkalinization to an optimal urinary pH of around 7.5 are alternative means to treat cystinuria during pregnancy. However, patients with high urinary excretion of cystine (ie, >300 mg/24 h) may need low-dose penicillamine treatment. Studies performed by Gregory and Mansell (1983) suggest that the risk of recurrent stone formation may outweigh the theoretical risks of penicillamine exposure in this particular situation.
Alpha-mercaptopropionyl glycine (alpha-MPG) is an alternative to penicillamine. It has the same mechanism of action and is roughly equal in efficacy, with somewhat fewer and milder adverse effects. Like penicillamine, it is contraindicated in pregnancy.
Surgical intervention is required in 20-30% of pregnancies complicated by urolithiasis. Surgical treatments are somewhat limited and are used to provide temporizing drainage of an obstructed system with placement of a ureteral stent or percutaneous nephrostomy, to delay treatment until completion of the pregnancy, or to definitively diagnose and treat the stone with ureteroscopic methods.
A broad spectrum of interventions, ranging from ureteral stent placement to open lithotomy, have been used to successfully treat urolithiasis in pregnancy ; however, regardless of the mode or invasiveness of the surgical intervention (eg, endoscopic, percutaneous, open), each carries an element of risk to the mother and fetus. Thus, surgical intervention is reserved for pregnant patients in whom conservative management fails or when surgery is otherwise indicated. Admission of these patients by the obstetrician service for consultation with a urologist is not unusual. As a result, most if not all, of these women undergo noninvasive fetal monitoring.
Indications for surgical intervention include the following:
Ureteral obstruction associated with increasing azotemia
Obstruction in a solitary kidney
Intractable pain despite maximal conservative measures
Renal colic–induced premature labor unresponsive to tocolytics
Traditional treatment has consisted of initial placement of a percutaneous nephrostomy tube or insertion of a ureteral stent for temporary drainage. Ureteral stents and/or nephrostomy tubes are then changed at periodic intervals until delivery, thus allowing delay of definitive treatment until completion of pregnancy.
Ureteroscopy is gaining favor as a first-line approach to urinary calculi that require intervention.[21, 34, 29, 23] Improved instruments and increased experience have led to successful outcomes with few complications. Disbanding of supposed limitations (anatomical distortion late in pregnancy) and resolution of many associated concerns (anesthesia, radiation) has resulted in advocacy from previous opponents.[35, 17] These significant changes represent a paradigm shift in intervention for urolithiasis in pregnancy unresponsive to conservative treatment.
Ureteral stent placement
Internal stents are usually placed with ultrasound guidance or limited fluoroscopy with local anesthesia. This minimizes risks of radiation and anesthesia to the fetus. Increasing oral hydration and decreasing calcium intake is recommended to prevent stent encrustation secondary to urinary stasis, hypercalciuria, or infection. Replacing stents every 3-4 weeks and antibiotic prophylaxis are suggested to avoid urinary tract infection and calcification. Insertion of percutaneous nephrostomy tubes or ureteral stents is considered a minor procedure, yet repeated insertions or changes may carry risks comparable with those of definitive ureteroscopy in a single setting. The obstetrician should be involved for fetal monitoring.
Ureteral stents often cause irritative voiding symptoms and chronic discomfort. The physiologic hydroureteronephrosis of pregnancy has been found to aggravate that by allowing more frequent stent migration within the dilated system. Parulkar and coworkers (1998) studied a group of 70 pregnant patients with urolithiasis; 19 patients required intervention, 15 of whom had ureteral stents placed. They reported that 5 of 15 patients (>30%) required subsequent manipulation because of migration, encrustation, or severe irritative symptoms.
Denstedt and Razvi (1992) recommend limiting ureteral stent placement until after 22 weeks of pregnancy, with use of a percutaneous nephrostomy prior to that point. If a ureteral stent is indicated but cannot be placed with ultrasound guidance or if urosepsis is present, a percutaneous nephrostomy tube should be placed instead.
Disadvantages to internal ureteral stent include the following:
Urinary tract infections and promotion of ascending infections
Irritative voiding symptoms and renal colic due to stent
Stent migration due to hydroureteronephrosis of pregnancy
Multiple procedures to change stent to avoid encrustation
Need for patient compliance and vigilant follow-up for stent change
Use this treatment modality in patients with urosepsis or pyonephrosis. This procedure can be performed with local anesthesia and ultrasound guidance. Nephrostomy tube placement allows for rapid and adequate decompression of the upper urinary tract, control of pain due to acute obstruction, and resolution of the infected hydronephrosis. Another advantage of placing a percutaneous nephrostomy tube is that it may be used for antegrade irrigation with an antibiotic solution to decrease the risk of infection and tube encrustation. Internalization of a double-J stent can be performed after recovery from the original illness. This procedure needs to be performed by a physician experienced in percutaneous procedures. Disadvantages to percutaneous nephrostomy include the following:
Bacteruria despite preventive antibiotics
Frequent obstruction, requiring change and/or flushing
Cumbersome external appliance
Risk of bleeding
Ureteroscopy and stone manipulation
Ureteroscopy allows for complete visualization of the entire ureter and renal pelvis, enabling accurate diagnosis and definitive treatment for urolithiasis. Anatomic distortion near the completion of pregnancy has long been thought to make ureteroscopy impossible; however, ureteroscopy has been found to be safe and effective in all stages of pregnancy.[21, 34, 29, 23] They also found that rigid ureteroscopy could be performed on the entire urinary tract, even in advanced pregnancy. The above group of series, along with the work of Lemos and associates , represent 68 patients who underwent ureteroscopy for diagnosis and/or treatment; no obstetrical complications were reported, and only one ureteral perforation was reported. The one perforation was treated successfully with a stent, and the child was born healthy at term.
Most ureteroscopies are performed in the absence of radiation. In the above studies, radiation was used sparingly in only a few patients; furthermore, Ulvik et al (1995) and Scarpa et al (1996) used no radiation. Physiologic hydroureteronephrosis of pregnancy allows entry of the ureteroscope under direct vision without dilation of the ureteral orifice; dilation is rarely performed.[4, 29, 23]
General anesthesia is rarely used. The vast majority of procedures have been performed with epidural or spinal analgesia with an element of sedation. Scarpa and coworkers (1996) performed ureteroscopies in five patients without anesthesia and used only neuroleptic anesthesia (fentanyl or propofol and atropine) in 10. Ulvik et al (1995) reports the use of sedation analgesia and feel that it may be preferred to spinal or general anesthesia. Both rigid and flexible scopes have been used successfully.
In a study by Rivera et al of 26 women with urolithiasis during pregnancy, the number of anesthetic events and the anesthesia time were no different in patients treated with temporizing stents than in those who underwent ureteroscopic stone extraction. In the ureteroscopy group, the median number of anesthetic exposures was 1.18 and the median total anesthetic time was 80 minutes. In the stent group, six of the 15 required multiple stent exchanges for a median of 1.47 anesthetic events and a median total anesthetic time of 70 minutes.
Kavoussi and associates (1998) suggest that definitive ureteroscopy may be preferable to stenting in select patients (particularly patients >6 wk prior to term). Ulvik and associates (1995) found a significant decrease in hospital stay among ureteroscopy patients (mean, 2.7 d) compared with ureteral stent patients (mean, 7 d) of Stothers and Lee (1992) .
Stone retrieval via ureteroscopy has been performed successfully in many forms.[40, 21, 29, 23] These include holmium YAG Laser, pulsed dye laser, ballistic lithotriptor, ultrasonic lithotriptor, basket retrieval, and forceps crush and retrieval; all were used successfully without known complications. The holmium YAG laser, with less than 1 mm of penetration, has been used most frequently in the more recent studies.[40, 21, 34] Ulvik and coworkers (1995) recommended against the use of the ultrasonic lithotriptor until further data can prove its safety in fear that the high-pitched noise may result in hearing injury to the fetus.
Akpinar and associates (2006) presented the most recent experience of ureteroscopy in 7 patients. The holmium laser was used with success in six patients and no stone was found in the seventh. They compared postoperative pain with or without a ureteral stent. They recommend routine stent placement with a string for 72 hours postoperation in order to reduce pain and analgesic requirements.
Contraindications to ureteroscopy include the following :
Stones larger than 1 cm
Ureteroscopic inexperience or inadequate instruments
Absence of general obstetrical services or high-risk obstetrical services
In the past, pregnant patients who required intervention for urolithiasis underwent open lithotomy or blind stone manipulation under general anesthesia, similar to the general population. However, more modern procedures used to surgically treat urolithiasis are performed without anesthesia or radiation and carry lower morbidity rates while maintaining equal or greater success rates. Consequently, open surgery is now used as a last resort. Open surgery is used if a stone must be removed before delivery because of complications of conservative or invasive management of urolithiasis, or if contraindications to ureteroscopy are present.
Percutaneous nephrolithotomy (PCNL), when indicated, is best postponed until postpartum because of the risks to the fetus of anesthesia and radiation.
Extracorporeal shockwave lithotripsy (ESWL) is frequently used in the nongravid population; however, it requires frequent use of ionizing radiation, and the potential adverse effects of energy dispersion on the fetus are unknown. At this time, ESWL is contraindicated during pregnancy.
Physiologic organ system changes increase specific perioperative risk factors in the pregnant patient. Special attention to these risk factors can help prevent associated morbidity to the mother and fetus.
Pregnancy-related changes in the cardiovascular and hematologic systems create a hypercoagulable state and place the patient at increased risk of venous thromboembolism and pulmonary embolism. The risk of venous thromboembolism is progressive throughout gestation and, in the third trimester, is estimated to be 5-6 times greater than that for a nongravid female.
The increasing size of the gravid uterus changes the hemodynamics in the lower extremities. Compression of the great vessels by the uterus reduces the velocity of venous blood return, increases pressure, and increases the risk of stasis in the lower extremities. Hematologic changes include increased plasma levels of clotting factors VII, VIII, and X and fibrinogen , as well as a decrease in fibrinolytic activity .
Low-dose heparin is considered safe and effective by some researchers and is recommended in patients with a history of thromboembolism.
Pregnancy-related changes in gastrointestinal function and relative anatomy increase the risk of inadvertent perioperative aspiration. These changes include compromised integrity of the gastroesophageal sphincter, decreased gastrointestinal motility, and a decrease in the pH of gastric secretions. Intravenous proton pump inhibitors provide acid suppression and may be used in the perioperative period as prophylaxis for acid aspiration syndrome during induction of anesthesia.
Fetal risks of anesthesia
Inhalation anesthetics readily cross the placenta because of their lipid solubility. These agents have been shown to increase risk of teratogenicity. General anesthesia should be avoided during the first trimester, after which the risk is minimal.
Management of pregnant patients with urolithiasis should always involve the obstetrician. When treatment beyond conservative measures is indicated, for the fetus' safety, coordinated care with a neonatologist, an anesthesiologist, and even a radiologist is appropriate.
Dietary modification is the cornerstone of preventing urolithiasis. General recommendations include dietary moderation of high-oxalate foods and purines with an increase in fluid intake. Salt and sodium intake should also be moderated because of their tendency to increase fluid retention and hypercalciuria. Low-calcium diets frequently cause a paradoxical rise in calcium stone formation and are discouraged.
Specific long-term dietary changes should ideally be based on objective information from the stone composition analysis and 24-hour urine chemistry determinations.
A low-oxalate diet tends to prevent calcium oxalate stone formation. Common foods that are high in oxalate include chocolate, nuts, green leafy vegetables, coffee, spinach, beets, and tea. Moderation and proportionate reductions are suggested rather than complete avoidance of high-oxalate foods that the patient enjoys.
While excessively high calcium ingestion is discouraged, unusually low-calcium diets can also increase stone production by allowing increased oxalate absorption from the gastrointestinal tract. Low calcium intake may also lead to a decrease in calcium bone deposition with associated osteopenia and osteoporosis. In general, one calcium meal per day is suggested. If a calcium supplement is being used by the patient, calcium citrate seems to be the least likely to increase calcium stone production because of a compensatory increase in urinary citrate excretion with this particular supplement.
Drinking at least 2 qt of water per day decreases the risk of stone formation. Actually, recommending a fluid intake sufficient to generate a 24-hour urine volume of 2000 mL per day may be better. A patient guide to maintaining an increased urinary volume developed by Stephen W. Leslie, MD, FACS, may be helpful. This recommendation includes stones of all types. In patients unable to drink the required amount of water, lemonade is a reasonable substitute. Lemon juice is high in citrate, which is a natural inhibitor of kidney stone formation.
A low-methionine diet has been reported to decrease the risk of cystine stone formation. Methionine is a dietary precursor of cystine. However, this diet is unpalatable, and patient compliance is poor.
Diets that are high in purines and green vegetables may increase the likelihood of stone formation. A low-purine diet decreases the risk of both uric acid and calcium stone formation. This diet requires avoidance of red meats, beef, chicken, fish and peanuts.
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