What is the appropriate diagnostic workup for flank pain in pregnancy?

From the Guidelines

Flank pain in pregnancy should be initially evaluated with ultrasonography to avoid radiation risk to the fetus.

Diagnostic Workup

• Ultrasonography is the imaging tool of choice in pregnant patients with flank pain, as it has reasonably good sensitivity for stone detection and does not harm the patient or fetus with ionizing radiation 1.
• Urinalysis, including assessment of white and red blood cells and nitrite, is recommended for routine diagnosis to rule out urinary tract infections 1.
• If the patient remains severely symptomatic and the ultrasound examination is unrevealing, a limited intravenous pyelogram or magnetic resonance imaging (MRI) may be considered to define the level of obstruction and identify potential stones 1.

Additional Considerations

• Physiologic hydronephrosis of pregnancy should be considered in the differential diagnosis of hydronephrosis in pregnant patients, as it occurs in >80% of pregnant patients, more commonly on the right than the left, and is generally seen beginning in the second trimester 1.
• Ureteroscopic stone removal may be considered as a diagnostic and therapeutic approach in pregnant patients with ureteral stones, with minimal tissue penetration and low morbidity 1.

From the Research

Diagnostic Workup for Flank Pain in Pregnancy

The diagnostic workup for flank pain in pregnancy involves a combination of clinical evaluation, laboratory tests, and imaging studies. The following are some key points to consider:

• Flank pain in pregnancy can have various etiologies, including pyelonephritis, trauma, and spontaneous adrenal hemorrhage 2
• The association between maternal hydronephrosis and flank pain symptoms is poor, and hydronephrosis should not be considered etiologic in the absence of other clinical evidence 3
• For patients presenting with flank pain and suspicion of nephrolithiasis, renal bladder ultrasound (RBUS) should be the initial diagnostic study 4
• If diagnostic uncertainty still exists, a non-contrast CT scan or MRI can be obtained 5, 6, 4
• MRI is a valuable diagnostic tool, especially in emergencies, as it avoids radiation exposure and can provide detailed images of the adrenal glands and other abdominal organs 5, 6
• Ultrasound can also be used to examine the adrenal gland regions, despite its supposed poor sensitivity 6

Imaging Studies

The following imaging studies can be used to diagnose the cause of flank pain in pregnancy:

• Ultrasound: can be used to examine the adrenal gland regions and detect fluid collection or swollen adrenal glands 6
• CT scan: can show enlarged, hypodense, and non-enhanced adrenal glands in cases of non-hemorrhagic adrenal infarction 6
• MRI: can provide detailed images of the adrenal glands and other abdominal organs, and is especially useful in emergencies to avoid radiation exposure 5, 6
• Non-contrast CT scan: can be used if diagnostic uncertainty still exists after RBUS 4

Laboratory Tests

The following laboratory tests can be used to support the diagnosis:

• Blood tests: can help identify underlying conditions such as hypercoagulable state or adrenal insufficiency 5, 2
• Genetic testing: can be used to identify genetic mutations that may contribute to the development of thromboembolic events, such as the MTHFR 677CC mutation 5