A 28-year-old woman, gravida 1 para 0, at 34 weeks gestation comes to the emergency department due to sudden-onset cramps in the right lower abdomen, sweating, nausea, and 2 episodes of vomiting within the past 3 hours. She has had some irregular contractions but no vaginal bleeding or leakage of fluid. Fetal movement is normal. The pregnancy has been uncomplicated, and the patient has no chronic medical conditions. Temperature is 37.5 C (99.5 F), blood pressure is 130/86 mm Hg, and pulse is 102/min. Fetal heart rate tracing shows a baseline of 155/min, moderate variability, multiple accelerations, and no decelerations. Tocodynamometer demonstrates irregular contractions every 7-15 minutes. There is mild tenderness to palpation over the right flank. The uterus is nontender and the cervix is closed. Urinalysis shows moderate blood but is negative for white blood cells, leukocyte esterase, and nitrites. Laboratory studies show a hematocrit of 32%, leukocyte count of 14,000/mm3, and platelet count of 220,000/mm3. Which of the following is the most appropriate next step in management of this patient?
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This woman at 34 weeks gestation has sudden-onset right lower abdominal cramps with associated diaphoresis, nausea, and vomiting. She has flank tenderness on examination and urinalysis reveals moderate hematuria. This presentation is highly suggestive of renal colic secondary to nephrolithiasis. In pregnancy, nephrolithiasis often occurs in the second and third trimesters due to progesterone-induced ureteral dilation and decreased peristalsis, which lead to urinary stasis. In addition, pregnancy is associated with increased urinary calcium excretion. These combined effects predispose pregnant women to stone formation.
Some patients with renal stones also experience irregular contractions due to the proximity of the uterus to the inflamed ureter because the uterus is sensitive and reactive to prostaglandins released from ongoing inflammation. The diagnostic imaging of choice for evaluating abdominal pain in pregnancy, especially if renal stones are suspected, is renal and pelvic ultrasonography, rather than CT scan, to avoid unnecessary radiation to the fetus.
(Choices A and F) This patient has no evidence of a urinary tract infection. Urinalysis is negative for nitrites, leukocyte esterase, and white blood cells. Although her serum white blood cell count is slightly elevated, this is very common in pregnancy and, without other indicators of infection (eg, fever), does not suggest an infectious process. Neither antibiotics nor urine culture is the best next step in management.
(Choice B) Preterm labor is regular, painful contractions leading to cervical change at <37 weeks gestation. This patient has irregular contractions (every 7-15 minutes) without cervical change, along with a nontender uterus (ruling out intrauterine infection). The tocodynamometer activity is related to pelvic inflammation, not preterm labor; therefore, uterine tocolytics are not indicated.
(Choice C) Abdominal radiography is of limited utility in diagnosing renal stones because it detects only radiopaque stones, misses small stones (of any composition), and does not detect hydronephrosis. Patient factors (obesity, constipation) can further decrease their sensitivity. In addition, x-rays expose the fetus to small amounts of radiation.
(Choice D) Coagulation studies would be indicated if disseminated intravascular coagulation secondary to placental abruption were suspected. Placental abruption causes acute-onset vaginal bleeding, abdominal pain, uterine tenderness, high-frequency contractions, and abnormalities on tocodynamic monitoring (eg, decelerations).
Educational objective:
Renal colic in pregnancy is associated with abdominal pain, flank tenderness, hematuria, and, often, irregular uterine contractions. Ultrasonography is the diagnostic imaging modality of choice for evaluating abdominal pain in pregnancy because it avoids radiation to the fetus.