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Prof. Dr. Ali Avanoğlu
UPJ Obstruction • Basics

Symptoms of UPJ Obstruction: How Is It Noticed in Infants, Children, and Adolescents?

UPJ obstruction most often causes no symptoms at all in infants and is noticed through a prenatal ultrasound. In older children and adolescents, episodic flank pain, nausea and vomiting, febrile urinary tract infection, blood in the urine, or a stone can be the first clue. This page walks through what to watch for at each age.

Who this is forFamilies whose child has unexplained abdominal or flank pain, vomiting, or febrile urinary tract infection, and parents following an infant with known hydronephrosis
Reading≈5 min
ByProf. Dr. Ali AvanoğluUpdated
This page is part of UPJ obstruction.Read the full treatment overview on the hub page
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kidney–ureter–bladder: SFU 3 hydronephrosis, narrowing at the UPJ (red ring) · flank pain wave
01 · What are the symptoms of kidney swelling?02 · In infants, it is mostly silent03 · In older children: episodic flank pain and vomiting04 · In adolescents and adults05 · Febrile urinary tract infection: a warning sign at every age06 · When you should see a doctor
In brief5 madde
  • What are the symptoms of kidney swelling?: Kidney swelling by itself often has no typical symptom of its own.
  • In infants, it is mostly silent: Today, most infants with UPJ obstruction are diagnosed without any symptoms at all, through kidney swelling (hydronephrosis) seen on a prenatal ultrasound.
  • In older children: episodic flank pain and vomiting: In children who can describe their symptoms, the most typical sign is episodic pain in the flank or abdomen.
  • In adolescents and adults: In adolescents and young adults, symptoms resemble those in childhood but are described more clearly: flank or back pain after exercise or a lot of fluid, a dull and…
  • Febrile urinary tract infection: a warning sign at every age: A widened, slowly emptying kidney is a favorable environment for bacteria to take hold.
01

What are the symptoms of kidney swelling?

Kidney swelling by itself often has no typical symptom of its own. The finding shows up on ultrasound, and since it usually causes no complaint in the child, the family notices nothing.

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  • The symptomatic picture, when it occurs, depends on the underlying cause of the widening. In UPJ obstruction, episodic flank pain, vomiting, febrile urinary tract infection, or blood in the urine are the leading findings.
  • The expectation that "more widening means more symptoms" is not accurate. A baby with severe widening may have no complaints at all, while a seemingly mild picture can still cause pain attacks; this is why follow-up is based on measurement and kidney function rather than on symptoms.
02

In infants, it is mostly silent

Today, most infants with UPJ obstruction are diagnosed without any symptoms at all, through kidney swelling (hydronephrosis) seen on a prenatal ultrasound. The baby feeds well, gains weight, and looks completely fine from the outside.

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  • This silence can be deceptive: the absence of symptoms does not mean the narrowing is unimportant. That is why widening detected before birth is followed with planned ultrasounds even when the baby looks well.
  • If no prenatal ultrasound was done, or the widening was missed, the baby may draw attention through febrile urinary tract infection, a palpable swelling in the abdomen, frequent vomiting and fussiness, or, rarely, blood in the urine. A large hydronephrosis can sometimes be felt as a soft mass in the baby's abdomen.
03

In older children: episodic flank pain and vomiting

In children who can describe their symptoms, the most typical sign is episodic pain in the flank or abdomen. The pain often starts after drinking a lot of fluid, a fizzy drink, or vigorous activity, lasts for hours, comes with nausea and vomiting, and then disappears completely.

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  • This picture results from intermittent obstruction and is called Dietl's crisis. Because the child is completely well between attacks, families and doctors often first suspect gastroenteritis (a stomach-and-bowel infection), constipation, or appendicitis.
  • Younger children cannot localize pain to the flank; they say "my tummy hurts" or point around the belly button. Recurring abdominal pain that comes with vomiting and fully disappears between episodes should bring kidney ultrasound to mind.
04

In adolescents and adults

In adolescents and young adults, symptoms resemble those in childhood but are described more clearly: flank or back pain after exercise or a lot of fluid, a dull and persistent heaviness, and sometimes visible blood in the urine. Compression from a crossing vessel is reported more often at this age.

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  • Stagnant urine makes stone formation easier; the first symptom can be a kidney stone or stone-related colic. In a kidney found to have both a stone and widening, whether an underlying narrowing is present is investigated separately.
  • In some adults the narrowing stays silent for years and is found incidentally on imaging done for another reason. In our practice, since Assoc. Prof. Dr. Issı also treats adult urology, adolescent and adult patients are evaluated by the same team.
05

Febrile urinary tract infection: a warning sign at every age

A widened, slowly emptying kidney is a favorable environment for bacteria to take hold. Febrile urinary tract infection (kidney infection, pyelonephritis) can be the first symptom of UPJ obstruction at any age and can run a more severe course in an obstructed kidney.

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  • If an infant's fever cannot be explained, a urinary infection is confirmed, and widening is seen on ultrasound, the infection is treated and the cause of the widening is investigated separately. Recurring febrile infection is one of the findings that pushes the decision toward surgery.
  • Whether prophylactic antibiotics are needed in an infant with hydronephrosis depends on the grade and the risk group.
06

When you should see a doctor

In a child with known hydronephrosis or UPJ obstruction, the situations below should be assessed without delay. This list is for information; when in doubt, call your doctor.

  • Fever (38°C / 100.4°F or higher) together with flank or abdominal pain, chills, or vomiting: same-day evaluation, because of the possibility of an infected obstructed kidney.
  • Severe, unrelenting flank or abdominal pain with vomiting: this may be a Dietl's crisis; an ultrasound taken while the pain is present confirms the diagnosis.
  • In a child with a solitary kidney, or with widening in both kidneys, a drop in urine output, swelling, or marked weakness.
  • Visible blood in the urine, or a baby who is not feeding or is drowsy.
  • Recurring, unexplained abdominal pain, or a second febrile urinary tract infection: not an emergency, but planned evaluation is needed.
UPJ Obstruction video guide3 short videos, in order
Frequently asked questions
My baby has no symptoms at all — is follow-up still needed?
Yes. In infants, UPJ obstruction most often causes no symptoms; what protects the kidney is regular monitoring with ultrasound. How often follow-up happens is set by the degree of widening, and intervals are spaced out further when the grade is mild.
Is my child's abdominal pain from UPJ obstruction?
Most childhood abdominal pain is not related to the kidneys. If the pain comes with vomiting, starts after a lot of fluid or activity, lasts for hours and then completely disappears, and recurs, a kidney ultrasound should be requested — preferably while the pain is present.
Does the severity of symptoms show how severe the narrowing is?
Not always. A kidney with severe widening can stay silent for years, while a narrowing that looks mild can still cause severe pain because of intermittent compression. That is why the decision is made together with symptoms, function, and the course over time — not from symptoms alone.
Does UPJ obstruction raise blood pressure?
Rarely, in long-standing and severe obstruction, kidney-related high blood pressure has been reported; it is not a common symptom in children. Blood pressure measurement is a routine part of the follow-up examination.
←Previous • BasicsWhy Does UPJ Obstruction HappenNext • BasicsDietl's Crisis→
Related pagesFull index →
BasicsKidney Swelling in InfantsKidney swelling (hydronephrosis) seen on a post-birth ultrasound is one of the most common urinary findings in infants, and most of it is temporary. This page explains the causes, the millimeter thresholds, the likelihood of it resolving on its own, and how follow-up works.BasicsDietl's CrisisDietl's crisis is an attack of severe flank/abdominal pain and vomiting that occurs when UPJ obstruction turns into intermittent complete blockage. The attack lasts for hours and then disappears entirely; between attacks the child, and often the ultrasound too, look completely normal. Because of this, it is frequently missed, and diagnosis relies on an ultrasound taken during the pain.Follow-up or surgery?Pain, Febrile Infection, or a StoneIn asymptomatic UPJ obstruction, the decision is usually based on numbers; once a symptom appears, the scale shifts. Recurrent flank pain, febrile urinary tract infection, and kidney stones are listed in guidelines under "symptomatic obstruction" as an indication for pyeloplasty. This page explains how each symptom feeds into the decision.BasicsWhat Is UPJ Obstruction?UPJ obstruction (ureteropelvic junction obstruction; informally, kidney outlet narrowing) is a narrowing at the point where the renal pelvis opens into the ureter. Urine passes through this point slowly, the pelvis widens, and this appears on ultrasound as hydronephrosis (kidney swelling). In most children it is congenital, and a large share can be followed without surgery.
UPJ Obstruction topic clustersMain treatment page →
Basics 7Diagnosis and evaluation 6Follow-up or surgery? 7Conservative follow-up 5Pyeloplasty and approaches 7After surgery and follow-up 6By age, and special situations 7
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