USA: A recent study published in the journal Frontiers in Surgery, reports a standardized care pathway for the management of nephrolithiasis during pregnancy. It contains multi-disciplinary guidelines from an academic medical center.
Nephrolithiasis management during pregnancy can be stressful for urologists owing to concerns for investigations and treatments poses a risk of fetal harm and unfamiliarity with optimal management of these complex patients. In response, multi-disciplinary evidence-based guidelines were developed to standardize the care for obstetric patients presenting with flank pain and suspicion for nephrolithiasis.
For developing the guideline, a multi-disciplinary team led by Matthew S. Lee, Department of Urology, University of Michigan, Ann Arbor, MI, United States, was assembled. A total of 11 guideline statements were constructed; four to guide diagnosis and imaging, and seven to guide intervention.
Initial workup/imaging
Recommendation 1
The management of the gravid patient with suspected symptomatic nephrolithiasis should emphasize a multidisciplinary approach, with early involvement of obstetrics, radiology, and anesthesiology teams. The on-call urology team and the on-call obstetrics (OB) team should also be notified when the patient first presents. The OB service can make recommendations regarding need for deep vein thrombosis (DVT) prophylaxis while patients are admitted.
Recommendation 2
The initial evaluation should include patient history, relevant obstetric and pregnancy history, physical exam, urinalysis with reflex urine culture, basic metabolic panel, and complete blood count. Fetal monitoring may be initiated based on gestational age as determined by the OB service.
Recommendation 3
RBUS should be the first-line imaging modality for obstetric patients presenting with renal colic suspicious for obstructing nephrolithiasis. Elements of a high-quality report include renal indices and evaluation of ureteral jets. Transvaginal ultrasound can be considered for more accurate imaging of distal ureteral stones.
Recommendation 4
If the diagnosis of obstructing nephrolithiasis remains uncertain and there is a change in clinical status of the patient that would otherwise necessitate interventional management, second-line imaging should be offered.
In the acute clinical setting (fever, hypotension, or considering intervention for intractable symptoms), a low dose non-contrast CT should be obtained.
In the non-acute setting, repeat RBUS, non-contrast MRI with HASTE, or non-contrast CT (NC-CT) should be discussed as second-line options. Ultimately, the next choice of imaging modality should be based on shared decision-making with the patient as there are risks and benefits to each, as discussed below. If the patient has already been exposed to multiple irradiating studies throughout the pregnancy, consultation with a medical physicist from radiology (if available) to help inform the clinical decision should be considered.
Intervention
Recommendation 5
If a patient's symptoms can be managed with analgesics and there are no complicating factors, a trial of passage with hydration and analgesia is warranted. Medical expulsive therapy appears to be safe. Patients failing medical expulse therapy should follow up with the Urologist to discuss ureteroscopy.
Recommendation 6
If there is a concern for septic obstructing stone, urgent collecting system decompression is required with ureteral stent placement, this recommendation holds regardless of gestational age. Stenting is safer for the patient and the fetus given that percutaneous nephrostomy (PCN) placement would require prone positioning (difficult to access airway and perform fetal monitoring). Furthermore, obstetric patients are at a high aspiration risk due to mechanical changes from the gravid uterus and the effects of progesterone including impaired gastric motility and lower esophageal sphincter tone.
Recommendation 7
When placed, ureteral stents should be exchanged every 4 weeks until definitive management is performed.
Recommendation 8
If conservative management fails, ureteroscopy with laser lithotripsy should be offered as a first-line treatment in non-complex scenarios.
Recommendation 9
Ureteroscopy during the third trimester may be associated with higher rates of pre-term labor, however it should not be excluded as a treatment option. When clinically prudent, the decision to proceed with ureteroscopy should be determined after a discussion between the patient, urology and obstetrics teams occur. The third trimester is from 28 to 40 weeks. Once at 32 weeks gestation, risks to the fetus quickly decline as the pregnancy progresses with similar long-term outcomes as a full-term neonate. Betamethasone for fetal lung maturation may be administered as well as magnesium sulfate for fetal neuroprotection.
Recommendation 10
If appropriate, neuraxial anesthesia (spinal, epidural, or combined spinal-epidural) is preferred over general anesthesia in obstetric patients given that the physiologic changes of pregnancy increase the incidence of aspiration and difficult airway management. Neuraxial anesthesia also limits fetal exposure to anesthetic agents and medications. However, these considerations do not preclude a patient from receiving general anesthesia when necessary and there is no clear evidence that it poses a greater risk to the fetus. The potential for difficult airway management and aspiration should be considered and anticipated when planning for any type of anesthetic.
Recommendation 11
Patients discharged to home with indwelling ureteral stents/PCN tubes or residual stones should have established outpatient follow-up with a urology provider and their obstetric provider. Definitive treatment with ureteroscopy can then be offered as an outpatient.
Reference:
Lee MS, Fenstermaker MA, Naoum EE, Chong S, Van de Ven CJ, Bauer ME, Kountanis JA, Ellis JH, Shields J, Ambani S, Krambeck AE, Roberts WW and Ghani KR (2021) Management of Nephrolithiasis in Pregnancy: Multi-Disciplinary Guidelines From an Academic Medical Center. Front. Surg. 8:796876. doi: 10.3389/fsurg.2021.796876