Obstructing ureteric stone at 24 weeks of pregnancy
A 31-year-old woman, gravida 2 para 1, at 24 weeks' gestation presents with 3 days of intermittent right flank pain radiating to the groin, nausea, and one episode of vomiting. She is afebrile (37.1 °C), heart rate 98/min, blood pressure 112/68 mmHg. She has no dysuria. Urinalysis shows 30–50 red cells per high-power field, no nitrite, and a few white cells. Serum creatinine is 0.7 mg/dL and white cell count 10.8 × 10⁹/L. Obstetric review confirms a healthy fetus with normal amniotic fluid. Ultrasound shows moderate right hydronephrosis and a 9-mm echogenic focus at the right vesicoureteric junction with shadowing. She has no previous stone history. She is anxious about radiation and asks whether she can "just wait until the baby is born". The department has ureteroscopy, holmium laser, and a radiology service that can provide low-dose CT.
1. What imaging would you use to confirm the diagnosis, and what are the limits of each modality?
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Ultrasound is first-line because it is safe and readily available. Here it is already diagnostic: moderate hydronephrosis with a 9-mm shadowing stone at the vesicoureteric junction. Physiological hydronephrosis of pregnancy can confuse the picture, but a stone at the vesicoureteric junction with obstruction is convincing.
If ultrasound were equivocal, MRI without gadolinium is the next safe option, although small stones may be missed. Low-dose CT can be used when necessary, with counselling and abdominal shielding, but it should not be the first test. In pregnancy, the principle is to answer the clinical question with the least radiation; a diagnostic ultrasound avoids radiation entirely. I would not repeat imaging simply to confirm a stone that is already clearly seen.
2. How would you manage the stone now, and what would you tell her about waiting until delivery?
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She has an obstructing 9-mm stone with pain but no fever or sepsis. Options are temporising drainage with a ureteric stent or nephrostomy, or primary ureteroscopy with laser lithotripsy. In an experienced centre, ureteroscopy is reasonable at 24 weeks: it offers definitive stone clearance, avoids repeated stent exchanges, and has a high success rate in pregnancy. I would use antibiotic prophylaxis, limit operative time, use holmium laser with low energy, position her with left lateral tilt, and arrange fetal monitoring. A stent is left post-operatively.
A stent or nephrostomy is preferred if there is infection, if ureteroscopy fails, or if the team lacks experience. Stents require exchange every 4–6 weeks because of encrustation and cause discomfort. Expectant management is risky: persistent obstruction can cause infection, preterm labour, and renal deterioration. I would tell her that waiting until delivery is not safe with a 9-mm obstructing stone and that intervention now is the safer choice.
3. What follow-up and definitive plan would you arrange after delivery?
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After delivery, the stent should be removed or exchanged and definitive stone treatment planned. She needs stone analysis and a metabolic screen: serum calcium, phosphate, uric acid, parathyroid hormone, and a 24-hour urine collection for volume, calcium, oxalate, citrate, and uric acid. A non-contrast CT will define residual stone burden. If the stone passed or was cleared, I would give dietary advice-high fluid intake, normal dietary calcium, reduced sodium-and follow up in a stone clinic.
The judgement point is that pregnancy-related obstruction is not the end of the episode. Recurrence is common, and a first stone in pregnancy warrants the same metabolic evaluation as in a non-pregnant patient, once breastfeeding is complete.