Williams Manual of Pregnancy Complications, 23 ed.

CHAPTER 66. Nephrolithiasis

Because of their predilection for men and older patients, renal and ureteral lithiasis are relatively uncommon complications of pregnancy, with an incidence of 1 in 2000 to 3000. Although women who have formed renal stones previously are at risk for doing so again, there is no evidence that pregnancy increases this risk. Moreover, stone disease does not appear to have any adverse effects on pregnancy outcome except for an increased frequency of urinary infections.

Calcium salts make up about 80 percent of renal stones, and in half of these, familial idiopathic hypercalciuria is the most common predisposing cause. Hyperparathyroidism should be excluded. Struvite stones are associated with infection, and often Proteus or Klebsiella is cultured from the urine. Uric acid stones are even less common.

DIAGNOSIS

Presumably, gravid women have fewer symptoms when they pass stones because of the urinary tract dilatation associated with normal pregnancy. However, we have observed that pain was the most common presenting symptom in 90 percent of women with nephrolithiasis, and only a quarter had gross hematuria. Persistent pyelonephritis despite adequate antimicrobial therapy should prompt a search for renal obstruction, which most frequently is due to nephrolithiasis.

Sonography may be helpful in confirming a suspected renal stone; however, pregnancy-related hydronephrosis may obscure this finding. If there is abnormal dilatation without stone visualization, then x-rays, such as the one-shot pyelogram, may be useful. Transabdominal color Doppler ultrasonography to detect absence of ureteral “jets” into the bladder has also been suggested in the workup of suspected urolithiasis.

TREATMENT

Management of the pregnant woman with nephrolithiasis depends on the symptoms and the duration of pregnancy. Intravenous hydration and analgesics are always given. Almost half of pregnant women with symptomatic stones have associated infection, which should be treated vigorously. In two-thirds of the cases, there is improvement with conservative therapy and the stone usually passes spontaneously. The other third require an invasive procedure.

In general, obstruction, infection, intractable pain, or heavy bleeding are indications for stone removal. Placing a flexible basket via cystoscopy to ensnare the calculus can be used in pregnant women. Other procedures include ureteral stenting, percutaneous nephrostomy, lithotripsy, transurethral laser ablation, and surgical exploration. Lithotripsy has replaced surgical therapy in many cases. This can be employed by extracorporeal means, percutaneous ultrasonic lithotripsy, or by ureteroscopic laser ablation of stones. Because stents for obstruction have to be changed every 4 to 6 weeks, some prefer lithotripsy in early pregnancy.


For further reading in Williams Obstetrics, 23rd ed.,

see Chapter 48, “Renal and Urinary Tract Disorders.”