The 5 Minute Urology Consult 3rd Ed.

PREGNANCY, UROLITHIASIS

Demetrius H. Bagley, MD, FACS

Kelly A. Healy, MD

 BASICS

DESCRIPTION

• The presence of calculi in the urinary tract during pregnancy can lead to severe risks and problems in management

• Urolithiasis is the most common cause of nonobstetric abdominal pain that requires hospitalization among pregnant patients

• Symptoms in urolithiasis can result in premature labor and fet al loss

• Stones with obstruction may lead to urosepsis requiring appropriate treatment

• Calcium phosphate most common followed by calcium oxylate

EPIDEMIOLOGY

Incidence

• Calculi in pregnant women occur at a rate of 1/1,500 pregnant patients; a rate similar to that of nonpregnant females (0.03–0.53%)

• Ureteral stones occur twice as often as kidney stones in pregnant patients

• Usually present in the 2nd or 3rd trimester

• Incidence—right vs. left side is similar

• Hispanics and whites more likely than blacks to develop stones during pregnancy

• Multiparous women are more commonly affected than are primiparous women

Prevalence

N/A

RISK FACTORS

• Dehydration

• Relative immobility

• Voluntary dietary modification (increased calcium)

Genetics

• Increased stone formation is likely with a positive family history

• Factors related to stone formation tend to group in families

• Women with known cystinuria should obtain genetic counseling and management of the stone disease before becoming pregnant

PATHOPHYSIOLOGY

• Several factors occur in pregnancy may enhance formation of stones:

– Pregnancy-induced urinary stasis

– Hypercalcemia and hypercalciuria

– Decreased ureteral peristalsis

– Physiologic hydronephrosis

 Starts 6–20 wk, in 90% by 3rd trimester

 Right side > left; may persist postdelivery

– Infection

• Associated higher incidence of maternal UTI (10–20%)

• Stone passage can precipitate premature labor and/or interfere with normal labor

• Controversial considerations may cause a higher rate of spontaneous abortions

• Physiologic dilation of calyces, ureters, and renal pelves begins in the 1st trimester and continues into the postpartum period

• Dilation is greater on the right than the left

• Decreased ureteral peristaltic activity because of hormonal and mechanical factors

• Dilation and decreased peristalsis allowed relative urinary stasis

• Increased urinary calcium excretion in pregnancy (↑2–3 times)

– Increased levels of 1, 25-dihydroxy vitamin D

– GFR increases 25–50% in pregnancy

• Urine is more alkaline in pregnancy and thus protective against uric acid stones

• Increase in excretion of stone inhibitors including citrate and magnesium

ASSOCIATED CONDITIONS

• Hydroureteronephrosis is the most significant renal alteration during pregnancy

• Physiologic dilatation of the collecting system begins in the 1st trimester and persists until 4–6 wk following delivery. This factor may also allow the passage of relatively larger calculi

• Increased urinary calcium excretion during pregnancy may present the major problem with indwelling stents and catheters

GENERAL PREVENTION

• Prophylactic measures to prevent the difficulties of treating urolithiasis during pregnancy should be considered

• Metabolic evaluation should be performed for known stone formers at a time when they are not pregnant and not lactating

• There should be consideration of treatment of asymptomatic stones prior to pregnancy

• As noted above, cystinurics have good management of the disease before becoming pregnant

 DIAGNOSIS

HISTORY

• Pregnancy history

• History of previous calculi

• Flank and back pain and changes in symptoms

• Dietary modifications

• Medications

• Voiding symptoms—urgency and frequency with urination

PHYSICAL EXAM

• Abdominal tenderness

• Tenderness at costovertebral angle

• Fever/chills

• Nausea/vomiting

DIAGNOSTIC TESTS & INTERPRETATION

Lab

• Urinalysis:

– Hematuria/pyuria

• Urine culture:

– UTIs are more common in pregnancy associated with stone disease (10–20%)

– A UTI can induce premature labor

• Serum creatinine:

– May be lower if the increased GFR (25–50%) in pregnancy

• CBC

Imaging

• Renal ultrasound (Standard initial imaging study in evaluation of pregnant patients) (1)

– Hydronephrosis

– Renal stones/proximal ureteral stones

– Extravasation/perirenal urinoma

– Abscess

– Resistive index (RI) >0.70 in intrarenal arteries supportive of acute obstruction

– No radiation exposure to fetus

• Transvaginal ultrasound

– Can demonstrate distal ureteral stones

– Can demonstrate ureteral jets, confirming urinary flow

– Document the diameters of distal ureter

• Noncontrast helical/spiral CT

– Although utilized increasingly in nonpregnant patients, delivers a relatively high radiation exposure

– Recent techniques have been decreased the radiation exposure

• Other imaging including standard excretory urogram and computerized tomographic scan are discouraged during the 1st and 2nd trimesters

– Abdominal radiographic and one excretory urogram has been widely used in pregnancy

– There has been no adverse effect of contrast material reported on the fetus

– Radiation exposure is the major concern

 Typical urogram gives <1.5 rads of exposure

 5–15 rads to the maternal pelvis in the 1st trimester increases the risk of congenital anomalies by 1–3%

 As little as 0.4–1.0 rads of fet al exposure can increase the risk of childhood malignancy 2.4 times

• MRI urography:

– Effect on fet al development poorly defined

– May be able to distinguish acute obstruction from the dilation of pregnancy

Diagnostic Procedures/Surgery

• The presence of ureteral calculi with obstruction is generally defined before interventional procedures

– Occasionally, the diagnosis is not certain and the presence of an obstructing calculus is defined only at the time of ureteroscopy

Pathologic Findings

N/A

DIFFERENTIAL DIAGNOSIS

• Acute pyelonephritis

• Appendicitis

• Cholecystitis

• Gastroenteritis

• Hydronephrosis of pregnancy

• Neurologic/musculoskelet al pathology

• Obstetric etiology of pain

• Other intra-abdominal conditions

• Renal vein thrombosis

 TREATMENT

GENERAL MEASURES

• Often misdiagnosed initially (appendicitis/diverticulitis/placental abruption)

• Conservative measures are taken initially to manage pain and infection so that the stone may pass (2)

• Hydration and analgesia, antiemetics and antibiotics are used

• Approximately 60–80% of renal calculi pass spontaneously. Among pregnant patients with dilated ureter, the passage rate is not defined

• Ureteral calculi associated with obstruction and upper tract infection demand immediate treatment with drainage and antibiotics

MEDICATION

First Line

• Narcotics including morphine, hydromorphone, butorphanol, meperidine, and acetaminophen can provide short-term pain relief without fet al harm

• Avoid codeine during pregnancy because of its association with fet al defects

• Nonsteroidal anti-inflammatory drugs are contraindicated because of the increased risk of miscarriage in the 1st trimester and other risks including fet al renal anomalies, fet al pulmonary hypertension and premature closure of the ductus arteriosus when used near term

• Medical management for the prevention of calcium stones should be delayed until after delivery

Second Line

N/A

SURGERY/OTHER PROCEDURES

• Intervention may be required in 20–30% of cases (3)

• Drainage may be necessary

• Cystoscopy/stent placement can be done with or without ultrasound guidance (4)

– Stents must be changed every 6 to 8 wk because of rapid encrustation in the pregnant women’s urine

• Percutaneous nephrostomy placement can be done under ultrasound:

– To minimize radiation exposure

– The stone or obstruction can be addressed postpartum

– The tube should be changed every 6–8 wk

– Clearly tube drainage alone must consider the duration of pregnancy

• Ureteroscopy with laser lithotripsy or impact lithotripsy has been very successful in treating stones in the upper urinary tract in the pregnant patient

• Shock wave lithotripsy has generally not been employed because of concerns of safety and the readily available alternatives

ADDITIONAL TREATMENT

Radiation Therapy

N/A

Additional Therapies

N/A

Complementary & Alternative Therapies

• Dietary changes including:

– Limiting high oxalate foods and purines

– Increase in fluid intake

– Limiting salt and sodium intake

– May be best preserved until metabolic evaluation postpartum

 ONGOING CARE

PROGNOSIS

Pregnancy outcome is not appreciably worsened because of symptomatic urolithiasis with appropriate management (5)

COMPLICATIONS

• Premature labor, fet al loss

• Urosepsis, renal insufficiency

FOLLOW-UP

Patient Monitoring

• During gestation:

– Conservative management with hydration

– Indications for intervention:

 Worsening renal function associated with persistent obstruction

 Intractable pain

 Obstruction of a solitary kidney

 Persistent infection associated with an obstruction

 Renal colic, precipitation premature labor that is refractory to treatment

– Preventive medications for stone disease have unacceptable side effects during pregnancy

 Thiazides: Can cause fet al thrombocytopenia, hypoglycemia, and hyponatremia

 Xanthanine oxidase inhibitors: No adverse effects on fet al animals but effects on human fetus known

 Penicillamine: Teratogenic in rats; fet al defects have been found in infants of mothers who took this during gestation

• Postpartum:

– Metabolic screening should be undertaken postpartum and should be delayed until completion of lactation period

Patient Resources

N/A

REFERENCES

1. Masselli G, Derme M, Laghi F, et al. Imaging of stone disease in pregnancy. Abdom Imaging. 2013;38(6):1409–1414.

2. Hoscan MB, Ekinci M, Tunç ran A, et al. Management of symptomatic calculi complicating pregnancy. Urology. 2012;80:1011–1014.

3. Bozkurt Y, Soylemez H, Atar M, et al. Effectiveness and safety of ureteroscopy in pregnant women: A comparative study. Urolithiasis. 2013;41:37–42.

4. Deters LA, Belanger G, Shah O, et al. Ultrasound guided ureteroscopy in pregnancy. Clin Nephrol. 2013;79(2):118–123.

5. Laing KA, Lam TB, McClinton S, et al. Outcomes of ureteroscopy for stone disease in pregnancy: Results from a symptomatic review of the literature. Urolo Int. 2012;89:380–386.

ADDITIONAL READING

Evan AP, Lingeman JE, Matlaga BR. Surgical management of upper urinary tract calculi. Urology. 2007;2:1456–1458.

See Also (Topic, Algorithm, Media)

• Pregnancy, Bacteruria, Pyuria, and UTI

• Pregnancy, Hematuria

• Pregnancy, Radiologic Considerations

• Pregnancy, Urinary Tract Obstruction

• Pregnancy, Urologic Considerations

• Pregnancy, Urologic Medications

• Urolithiasis, Adult General

• Urolithiasis, Ureteral Calculi Algorithm 

 CODES

ICD9

• 592.1 Calculus of ureter

• 592.9 Urinary calculus, unspecified

• 646.80 Other specified complications of pregnancy, unspecified as to episode of care or not applicable

ICD10

• N20.1 Calculus of ureter

• N20.9 Urinary calculus, unspecified

• O99.89 Oth diseases and conditions compl preg/chldbrth

 CLINICAL/SURGICAL PEARLS

• Most urinary stones pass.

• Intractable pain or infection with obstruction may necessitate drainage.

• Catheters, ureteral stent, or percutaneous nephrostomy (must be changed frequently at 4 to 6 wk because of the risks of encrustation).

• Ureteroscopic treatment with endoscopic lithotripsy appears to be the most efficacious and possibly safest treatment.



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