UPJ Obstruction: Follow-Up or Surgery? How the Decision Is Made

Parents often focus on one value in a report: "function came back 38%," "T½ is 25 minutes," "it says SFU 4." But current guidelines (EAU/ESPU 2024) recommend that the surgical decision in UPJ obstruction be made not from a single threshold but by interpreting several findings together.

The EAU/ESPU guideline lists the following situations for pyeloplasty; none is an automatic decision on its own — when several come together, the scale tips clearly toward surgery.

• Symptomatic obstruction: recurring flank pain attacks (Dietl's crisis), or febrile urinary tract infection.
• Split (differential) kidney function below 40% on MAG3 diuretic renography (a kidney scan); when confirmed on two measurements, surgery is considered more strongly.
• A drop in function of more than 10 points on serial measurements (confirmed with a repeat measurement).
• Poor drainage after the diuretic (furosemide) — not on its own, but together with declining function, increasing widening, or symptoms.
• A marked and progressive increase in the AP (front-to-back) diameter on ultrasound (jumping a category).
• High-grade hydronephrosis at SFU 3–4 or UTD P3 — especially if accompanied by parenchymal thinning.

A significant portion of UPJ-type hydronephrosis found in infancy is followed without surgery. The literature reports that only roughly a quarter (20–30%) of children with SFU 3–4 hydronephrosis eventually need pyeloplasty, while the majority either improve with follow-up or stay stable. Improvement and stabilization are usually seen in the first 2–3 years.

A single ultrasound or a single scan does not say where the kidney is heading — it only gives a snapshot of that day. When two snapshots of the same kidney taken 3–6 months apart are compared, the trend becomes visible: is the widening increasing, is function stable, has drainage changed.

In this conversation, your doctor lays out the findings together: what's on each side of the scale, which finding is borderline, and what to expect over what period of time. If follow-up is chosen, the answer to "what change would bring us back to surgery" is discussed up front; if surgery is chosen, the method (open, laparoscopic, robotic) is determined by the child's age and the center's experience.

• Fever (38°C / 100.4°F or higher) together with flank or abdominal pain: suspected infection in an obstructed kidney, same-day evaluation.
• Severe, unrelenting flank or abdominal pain with nausea and vomiting.
• In a solitary kidney or two-sided hydronephrosis, a drop in urine output, swelling, or weakness.
• A baby who cannot feed, is drowsy, or has visible blood in the urine.

• In our practice, this decision is made through the joint assessment of two pediatric urology specialists; the same team carries the process from diagnosis through follow-up. In the situations below, however, you should come in without waiting for the planned schedule.