Pelviureteric Junction Obstruction or PUJO is a condition in which the flow of urine from the kidney into the ureter is blocked or obstructed.

The urinary system consists of the kidneys, the ureters, the bladder, and the urethra. The kidneys filter out solutes from the blood and form urine. This urine passes into the calyces (singular: calyx) of the kidney and then into an area called the renal pelvis. The renal pelvis is the last part of the kidney where urine collects before it passes into the ureter. The ureter is a muscular tube that carries urine from the kidney to the urinary bladder.

The junction of the renal pelvis and the ureter is called the pelvic-ureteral junction (PUJ; or UPJ in some countries). Ordinarily, urine from the renal pelvis passes across the PUJ and into the ureter very easily. Therefore the renal pelvis is normally a collapsed and small structure. In some children, the PUJ is narrow and tight, not allowing the urine to pass easily. This is called PUJ Obstruction (or PUJO). Since the urine cannot pass into the ureter, it gets backed up in the renal pelvis, causing it to dilate. When the obstruction is significant, the calyces begin to dilate as well. This dilation of the renal pelvis with or without dilation of the calyces is called hydronephrosis. Over time, the pressure of the backed-up urine compresses the parenchyma, or the “functioning flesh” of the kidneys, and affects its ability to perform. If left untreated, the pressure from the backed-up urine could result in the kidney loses its ability to function.

Nowadays, PUJO is usually suspected when the baby is in the mother’s womb. It is the most common cause of antenatal hydronephrosis needing treatment. In some children, the PUJ may be adequate to allow urine across it when the baby is born, but as the baby grows and the kidney begins to produce larger volumes of urine, the PUJ cannot keep up. Thus the obstruction becomes manifest when the child is older. These children may complain of pain in the belly or side, or their parents might notice a lump in their belly. Sometimes, these children develop urinary tract infections. The problem comes to light when ultrasonography is done for these symptoms.

Ultrasonography provides adequate imaging to strongly suspect a PUJ obstruction. If the pediatric surgeon suspects a PUJO, he or she will most likely order another test called renal scintigraphy. Renal scintigraph (sometimes referred to as just a renal scan) is a nuclear medicine test that tells us more about the flow of urine through the urinary system. In this test, a radioisotope is administered intravenously. The body naturally filters the isotope in the kidney and then expels it into the urine. The presence of the radioisotope in the body is picked up by the gamma camera and converted into an image. If there is a PUJ obstruction, we can visualize the radio-isotope (and therefore the urine) being held up in the pelvis and not passing into the ureter easily. This is very important to help us differentiate an obstructed PUJ from a kidney that is dilated but not obstructed. The best radiotracer for isotope scans for children is MAG3. At most centers in India, an equivalent of MAG3 called EC is used. Other radiotracers include DTPA and DMSA. A radioisotope scan must be done in a child who is not younger than 6 weeks old. However, MAG3 and EC scans can be done in younger infants with good reliability.

In some cases, the surgeon may advise an MRI of the kidneys (called MR Urography) to delineate the exact anatomy of the obstruction. This is especially true in complicated cases, in patients who have undergone previous surgery, and in cases where compression of the PUJ by an external structure (most commonly a blood vessel) is suspected. MR Urography is becoming more popular as a diagnostic tool for PUJ obstruction.

Other tests include a urine test to make sure that there is no urinary infection and blood tests. In some cases, a special X-ray called an intravenous pyelography (IVP) or a CT scan (CT Urography) may be ordered, but these are falling out of favor because of concern for radiation.

In most cases, PUJ obstruction is diagnosed before birth, because it causes a dilatation in the urinary tract, which can be seen on prenatal scans. However, it is possible to get a PUJ obstruction later in childhood or even in adulthood, in which case symptoms can include a sharp flank pain accompanied by nausea and vomiting; urinary tract infections; or swelling in the abdomen.

To make a diagnosis, a radiologist will carry out an ultrasound scan of the kidneys and bladder. If your child has a PUJ obstruction, the ultrasound usually shows a swelling, or dilatation, of the kidney, and in some cases a thinning in the outermost layer of the kidney which is being compressed by the increased pressure.

The next stage is to carry out a MAG-3 renogram, which is a more specific test to assess the function and drainage of the affected kidney.

If the diagnosis is still not confirmed, other options include an MRI of the urinary tract or a retrograde pyelogram to see the urinary tract anatomy and urine drainage more clearly.

PUJO is treated by surgically removing the obstruction to the flow of urine.

Pyeloplasty (pronounced PIE-low-Plast-ee) is a surgery performed to relieve obstruction between the kidney and the upper part of the ureter. It is a reconstructive urologic procedure and is a common operation performed by paediatric surgeons and paediatric urologists.

Most pyeloplasties can be done by minimal access techniques through tiny incisions that heal quickly. Alternatively, conventional techniques can be used. Thus, the various approaches to performing a pyeloplasty include:

Dorsal lumpectomy: This technique can be used in infants and very young children whose back muscles are relatively thin. In this technique, the kidney is approached through an incision about 2 to 3 cm in length on the child’s back. The incision is horizontal so that the scar can be hidden reasonably well along the skin lines. When done correctly, the muscles need not be cut across their belly, but they do need to be split apart. The child needs to be placed face-down on the operating table for this surgery.

Flank incision or flank approach: This is a conventional technique used in older children. As any child who walks will have thicker back muscles than an infant, the dorsal lumpectomy approach becomes difficult. An incision is made on the child’s flank or side just below the rib cage. The Muscles are cut in order to reach the kidney. The subcostal nerve needs to be protected while making this incision. Some patients develop a flank bulge or a “phantom hernia” after this type of incision.

Laparoscopic Approach: This is arguably the most popular approach to pyeloplasty in children. This is a minimal access technique where the entire surgery is performed through 3 or 4 tiny incisions, none bigger than 5mm. When such tiny incisions are made the muscles need not be cut. In infants, 3 mm incisions are used. The surgery performed on the kidney is the same. However, since the incisions are tiny and the amount of dissection required is much less than in conventional surgery, the post-operative pain is significantly lower and recovery is much faster. An added bonus is a superior cosmetic outcome.

Robot-Assisted Laparoscopic Pyeloplasty: This is the latest technology in the arsenal of a paediatric surgeon. In a robot-assisted (or robotic) pyeloplasty, the operation is performed through tiny incisions just as in laparoscopy. However, instead of conventional laparoscopic instruments, the paediatric surgeon uses robotic instruments to perform the surgery. These instruments are completely controlled by the surgeon but they provide greater maneuverability and finer movements than conventional laparoscopic instruments. This allows the surgeon to sew the kidney and the ureter together with much more ease. As in laparoscopy, recovery is hastened and pain is significantly less. Robotic pyeloplasty is becoming an increasingly popular option all over the world.

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