Pelviureteric junction obstruction

　　1. Etiology

　　Although there have been in-depth studies from different perspectives such as embryology, anatomy, and histology, the exact etiology of UPJO is not yet fully clear. There are many causes of UPJO, and the etiology of UPJO can be summarized into 3 categories through gross and microscopic observation.

　　1. Intraluminal factors:Intraluminal intrinsic factors mainly include UPJ stenosis, valves, polyps, and high ureteral orifice. Among them, stenosis is a common cause of UPJ obstruction (accounting for 87.2%), mainly manifested as muscular layer hypertrophy and fibrous tissue proliferation at the UPJ. The stenotic segment is generally about 2cm long, with a cross-sectional diameter of only 1-2mm, often accompanied by a high ureteral orifice. The UPJ valve is a congenital fold that can contain muscle. Polyps are often in the shape of a sunflower.

　　2. Extraluminal factors:The most common cause is the wandering or accessory blood vessels originating from the main renal artery or abdominal aorta, crossing the UPJ to compress it and suspend the ureter or pelvis above the blood vessels. In addition, there are fibrous bands that compress or adhere, causing the UPJ to twist or attach at a high position.

　　3. Functional obstruction:It is manifested as dynamic functional disorder at the UPJ. Its characteristics are that there are no obvious intraluminal stenosis and extraluminal compression factors at the UPJ, and the ureteral catheter can pass smoothly during retrograde urography, but there is significant hydronephrosis.

　　2. Pathogenesis

　　The functional unit of the pelvis and ureter is the muscle cell, and from the renal papilla to the pelvis and ureter, it is possible to see bundles of fusiform smooth muscle cells arranged. Between the muscle cells, there are pale longitudinal arranged initiating cells that are closely connected with the muscle cells and communicate with each renal papilla. These cells can spontaneously or after receiving pressure from within the pelvis, send information to cause muscle contraction. When the muscle cells in this area have congenital defects or are damaged and destroyed, it will affect their normal contraction function, causing obstruction. Noeley observed through an electron microscope that the ureter near the dilated pelvis part has formed a non-elastic collar-like change due to significant collagen tissue proliferation, and believed that this is the initial cause of the narrowing at the pelvis and ureter junction. Subsequently, some scholars further observed through an electron microscope that the smooth muscle cells at the lesion site are separated from each other, gap junctions are broken, there is excessive intracellular matrix, and mitochondria show vacuolar degeneration. These pathological changes hinder intercellular information transmission, causing dysfunction of the smooth muscle at the pelvis and ureter junction. Therefore, it is believed that muscular layer developmental defects are the main cause of obstruction at the pelvis and ureter junction. Some scholars also propose that mechanical obstruction and functional damage may be mutually causal. Under normal circumstances, the coordinated movement of the pelvis and ureter junction can allow urine to pass smoothly through the pelvis and ureter junction. Local narrowing or peristalsis conduction disorders at the pelvis and ureter junction can cause urine retention, leading to hydronephrosis. The outcome of hydronephrosis after obstruction depends on the severity of the obstruction, the compliance of the pelvis and renal papillae, and urine flow. If a certain relative balance is reached, the progression of hydronephrosis will slow down and remain in a stable state for a certain period of time. Otherwise, hydronephrosis will further worsen. The expansion of the renal collecting system can cause elongation of renal medullary vessels and compression ischemia of renal parenchyma, leading to gradual atrophy and sclerosis of renal tissue, which is not completely reversible.

　　It often occurs with other malformations such as single kidney, horseshoe kidney, contralateral hydronephrosis, and multilocular renal cystic change.

　　1. Single kidney:It refers to the condition where a person is born with only one kidney, which is congenital. Normally, humans have two kidneys, but usually only one kidney is functional, so a single kidney does not cause significant impact on life (except for those with kidney disease), and it does not exclude the possibility of unknown effects, such as decreased immunity. If everything is normal, a person may not need to undergo any related examination throughout their life, and the single kidney may never be discovered. Therefore, as long as there is no kidney disease, there is no need to worry about the adverse effects of a single kidney on the body.

　　2. Fusion of the upper or lower poles of the bilateral kidneys to form a horseshoe kidney:The incidence rate is 1/500 to 1000, with a male-to-female ratio of 4:1. The horseshoe kidney occurs in the early embryonic stage, resulting from the fusion of the two renal buds of the embryo being tightly compressed between the umbilical artery. This condition was first discovered by Decarpi in 1521 during an autopsy, Botallo (1564) provided a comprehensive description with illustrations, and Morgagni (1820) reported the first case of a horseshoe kidney patient with complications.

　　3. Hydronephrosis on the contralateral side due to renal tuberculosis:It is a late complication of renal tuberculosis, caused by obstructive lesions of bladder and ureteral tuberculosis. It mainly affects the urinary drainage of the contralateral kidney through various pathological changes, leading to hydronephrosis and pyelonephrosis of the contralateral kidney and ureter.

　　4. Multilocular renal cystic change:They constitute the most common abdominal masses in neonates and young infants, mostly unilateral, without familial tendency, and without significant gender differences. The affected kidney loses its normal shape and is occupied by irregularly lobulated cysts, with varying sizes and numbers.

　　1. Abdominal mass:In neonates and infants, abdominal painless masses are often presented as clinical symptoms, with palpation revealing a cystic feeling, smooth surface, no tenderness, and a history of changes in mass size in some patients.

　　2. Pain:Except for infants, the vast majority of children can describe upper abdominal pain and umbilical pain, and abdominal pain is mostly intermittent and accompanied by vomiting, which is very similar to gastrointestinal diseases. The appearance of lumbar pain after drinking a lot of water is a major characteristic of the disease, which is pain caused by the sudden expansion of the renal pelvis due to diuresis. In addition, it can also be caused by the movement of the associated stones or the obstruction of blood clots.

　　3. Hematuria:The incidence of hematuria is about 10% to 30%, which can be caused by increased intrapelvic pressure, renal medullary vascular rupture, or caused by infection or calculus.

　　4. Infection:Urinary tract infection is more common in children, and once it occurs, the condition is serious and difficult to control, often accompanied by systemic toxic symptoms such as high fever, chills, and sepsis.

　　5. Hypertension:Hypertension can occur in both children and adults, which may be due to an increase in renin secretion caused by compression of renal blood vessels.

　　6. Renal destruction:Renal destruction is mostly traumatic, often leading to acute peritonitis.

　　7. Uremia:Because this disease often complicates other urinary system malformations, or because of bilateral hydronephrosis, late stage may have renal insufficiency, such as anuria, anemia, growth and development delay, and anorexia, and other symptoms of digestive system disorder.

　　The etiology is not yet clear, and there is no definite preventive measure. After the diagnosis is clear, it should be removed as soon as possible and actively prevent and treat urinary tract infection.

　　Prevention

　　Many researchers agree that early treatment is feasible and effective for restoring potential renal function, especially for children under one year old, where renal function damage is often less than 45%. If diagnosis is not made until adulthood, severe chronic obstruction often leads to progressive renal function damage. Poor drainage of urine and recurrent infections often form stones. Even in older patients, renal pelvisoplasty can be used to save the situation. Patients with poor renal function (10% to 25%) can also achieve partial recovery after surgery. A few patients with severe renal function damage may need nephrectomy.

　　1. Urinalysis:There may be microscopic hematuria or gross hematuria, and when complicated with infection, there may be pus cells, and urine culture may have pathogenic bacteria.

　　2. When renal insufficiency occurs, blood urea nitrogen and creatinine can increase.

　　3. Ultrasound examination:Ultrasound examination is simple, non-invasive, and diagnostic, making it the preferred examination method. Ultrasound examination can grade hydronephrosis, make an initial differentiation of the diagnosis of the obstruction site and the nature of the lesion, and is of great significance for estimating the reversibility of the renal function. Doppler ultrasound reflects the changes in renal blood flow by the frequency spectrum of renal intravascular blood flow, and determines the resistance index (resistance index, RI), which can help differentiate obstructive and non-obstructive hydronephrosis. Ultrasound examination of fetal urinary tract obstruction is more advantageous, and prenatal ultrasound examination can make an early diagnosis of congenital hydronephrosis.

　　4. X-ray examination:Abdominal X-ray examination can understand the size of the renal outline, and can make a definite diagnosis for X-ray positive calculi. If the hydronephrotic kidney or the proximal urinary tract obstructed can be visualized during excretory urography, it can make an evaluation of the obstruction site and renal function, especially it is more important for the judgment of the function of the divided kidney. For those who do not show up in IVU and cannot perform retrograde pyelography, percutaneous renal puncture urography can be performed [magnetic resonance urography (MRU) can be used instead].

　　5. Dynamic imaging examination:Diuretic renal imaging is very helpful in identifying early lesions and determining whether mild hydronephrosis requires surgical treatment, especially when there is one side lighter and one side heavier on both sides of the hydronephrosis, which has a decisive role in whether surgical treatment is needed for the side with less hydronephrosis.

　　In recent years, the application of diuretic B-ultrasound and synchronous video monitoring with diuretic intravenous urography has played a significant role in distinguishing obstructive and non-obstructive hydronephrosis from diuretic renal scintigraphy.

　　6. Magnetic Resonance Imaging (MRI):In recent years, MRI has been widely used in the diagnosis of urinary tract obstruction diseases, especially MR urography (MRU) is very helpful for the localization and qualitative diagnosis of obstruction. Its imaging is similar to that of urinary tract造影, and since MRU does not require the use of iodinated contrast medium and catheterization techniques to display urinary tract conditions, it is safe for patients, non-traumatic, and without complications, especially suitable for patients with severe renal dysfunction and urinary tract obstruction.

　　7. Pelvic pressure test:That is, place two catheters in the pelvis and bladder separately, inject contrast medium at a speed of 10ml/s through the percutaneous nephrostomy tube, and record the changes in intrapelvic pressure under the fluorescence screen during the injection of contrast medium to determine the pressure difference between the pelvis and bladder as an indicator of renal obstruction. If the pelvic pressure is greater than 1.37kPa (1410cmH2O), it indicates the existence of obstruction. This method is helpful for determining whether there is obstruction at the pelviureteral junction, but it is complex and traumatic, and is rarely used in clinical practice.

　　1. What foods are good for the body with pelviureteral junction obstruction

　　Eat light and easily digestible foods, fresh vegetables and moderate amounts of fruit, and drink enough water. Pay attention to a balanced diet.

　　2. What foods should be avoided for pelviureteral junction obstruction

　　Avoid overeating and eating unclean food. Avoid seafood, beef, mutton, spicy and刺激性 food, alcohol, and all kinds of irritants such as five-spice powder, coffee, coriander, etc. Avoid all kinds of tonics, tonics, and easy-to-heat food such as chili, chocolate, etc.

　　(The above information is for reference only. For details, please consult a doctor.)

　　First, treatment

　　The main purpose of treating pelviureteral junction obstruction is to relieve obstruction and protect the function of the affected kidney. The treatment methods mainly include open surgery and endoscopic surgery. The former mainly includes segmental pyeloplasty, Y-V plasty (Foley technique), and pyeloplasty with pyelopelvic flap (Culp technique), etc.; while the latter includes laparoscopic pyeloplasty, percutaneous nephrostomy and pyelotomy, ureteroscope pyelotomy, balloon dilation, etc. The specific method selection should be based on the patient's age, the cause, length of pelviureteral junction obstruction, thickness of renal parenchyma, degree of pyelocaliceal dilatation, whether there are other malformation factors, and whether there are conditions for endoscopic surgery. For patients with mild hydronephrosis and no obvious dilatation of renal calyces, surgery is not required at present. It is only necessary to control or prevent infection and to follow up regularly. If surgery is used unilaterally, it may lead to new problems such as local scar stenosis at the anastomosis and secondary infection, which may not be effective. The indications for surgical treatment are: obvious clinical symptoms, clear obstruction, some damage to the function of the affected kidney, and complications such as stones, infection, hypertension, etc. The operation of nephrectomy should be done with extreme caution, only when the thickness of the renal cortex

　　1. Open renal pelvis-ureteral reconstruction:In most cases, the treatment method adopted is dismembered renal pelvis reconstruction. Since this surgery can remove the diseased renal pelvis-ureteral junction and the redundant renal pelvis wall, establish a funnel-shaped renal pelvis and ureteral junction, restore muscogenic peristalsis, and has significant efficacy, the success rate of the surgery is as high as 85%-90%. Therefore, it is hailed as the 'gold standard' for the treatment of renal pelvis-ureteral junction obstruction. Other types of open surgeries such as Y-V plasty and renal pelvis flap renal pelvis reconstruction are less commonly used. The key points and precautions for dismembered renal pelvis reconstruction are as follows:

　　(1) Hydronephrosis caused by obstruction at the renal pelvis-ureteral junction is generally easy to separate due to the lack of tissue adhesions around the area, except when there is a large amount of hydronephrosis or recurrent infection. Therefore, surgery can be performed using a small incision.

　　(2) It is not sufficient to simply relieve mechanical compression caused by wandering vessels, fibrous bands, etc. Instead, further excision of the damaged part of the renal pelvis and the renal pelvis-ureteral junction should be performed to reconstruct a funnel-shaped renal pelvis, thereby improving the success rate of a single surgery.

　　(3) To prevent misalignment of the incision during the trimming and suturing of the renal pelvis wall, which may affect the transmission of peristaltic waves, it is recommended to pre-suture three marker lines at the superior, middle, and inferior margins of the renal pelvis incision using a round needle and silk thread after exposing the renal pelvis; and also to suture one marker line on the ureteral wall at the distal end of the stricture.

　　(4) Excise the redundant renal pelvis at a distance of 1-2 cm from the renal parenchyma, and try to minimize the renal pelvis capacity. Then, make a diagonal incision below the stricture to cut the ureter, and longitudinally incise the ureteral wall 1-1.5 cm on the lateral side of the ureter. Suture the V-shaped tip below the renal pelvis to the lower end of the ureteral incision using 5-0 Dexon suture in a full-thickness, interrupted manner, with a needle spacing of 2mm. During suturing, accurate alignment is required, with minimal mucosal suturing and maximal muscular and adventitial layer suturing.

　　(5) In patients with massive hydronephrosis, due to the dilatation of the renal pelvis, the residual cavity is large, which is prone to cause poor urine drainage, leading to infection. Therefore, it is recommended to perform a renal plication procedure during renal pelvis reconstruction to reduce the intrapelvic cavity size, improve urine emptying ability, and help with renal function recovery.

　　(6) Placing a ureteral stent and performing a temporary urinary diversion by renal pelvis stenting can prevent urinary extravasation, urinoma formation, and scar tissue formation, reduce the occurrence of secondary stricture; in addition, it can also prevent recurrence of obstruction caused by early postoperative ureteral intubation. Currently, the double-J catheter drainage placed in the ureter is commonly used to replace the traditional renal pelvis stenting and external ureteral stent. For patients with double-J catheter drainage, a urinary catheter is left in place for 5 to 7 days postoperatively to maintain low pressure in the bladder, avoiding urine reflux and affecting the healing of the anastomosis. The double-J catheter is removed 4 to 6 weeks postoperatively, and imaging follow-up is performed 3 to 6 months later.

　　2. Endoscopic Pyeloureteroplasty:With the improvement of endoscopic surgical instruments and techniques, the success rate of endoscopic treatment for renal pelvis and ureteral junction obstruction has gradually approached that of open surgery. Endoscopic surgery has the advantages of minimal trauma, rapid recovery, and fewer complications, and is expected to become the first-line treatment for adult renal pelvis and ureteral junction obstruction, especially suitable for those who are weak and cannot tolerate open surgery. Common endoscopic procedures include laparoscopic pyeloplasty, percutaneous nephrostomy for pyeloplasty, and ureterorenoscopy for pyeloplasty. However, it is not advisable to perform endoscopic pyeloplasty if the length of the narrowed segment is over 2 cm or there are ectopic vessels.

　　(1) Laparoscopic Pyeloplasty: Laparoscopic pyeloplasty is a new technique for treating renal pelvis and ureteral junction obstruction that was developed in 1993. It can be performed via an abdominal approach or an extraperitoneal approach; the operative technique under the laparoscope is basically the same as that of open surgery. Under the laparoscope, it is possible to accurately excise the redundant renal pelvis wall, complete the anastomosis between the lower renal pelvis and the ureter, and handle crossing wandering vessels and perform renal fixation; the success rate of the surgery is as high as 97%. It is particularly suitable for patients who have failed endoscopic pyeloplasty. Common endoscopic procedures include laparoscopic pyeloplasty, percutaneous nephrostomy for pyeloplasty, and ureterorenoscopy for pyeloplasty. However, it is not advisable to perform endoscopic pyeloplasty if the length of the narrowed segment is over 2 cm or there are ectopic vessels.

　　(2) Percutaneous Nephrostomy for Pyeloplasty: Also known as antegrade endoscopic pyeloplasty. The operation is performed by inserting a guide wire retrogradely through the cystoscope into the renal pelvis, then performing percutaneous nephrostomy under X-ray or B-ultrasound guidance, and placing a percutaneous nephroscope through the stoma. Under direct vision, the narrowed segment of the renal pelvis and ureteral junction is longitudinally incised through the full thickness of the posterior lateral wall of the ureter with cold knife, electrocautery, or holmium laser instruments, until the fatty tissue is seen. A double-J stent is placed along the guide wire to the bladder postoperatively, and a nephrostomy tube is also left in place. The nephrostomy tube is usually removed 1 to 3 days postoperatively, while the double-J stent needs to be left in place for 3 to 8 weeks.

　　(3) Ureterorenoscopy for Pyeloplasty: Also known as retrograde endoscopic pyeloplasty. The operation is performed by inserting a ureteroscope through the urethra, then ascending through the ureteral orifice to the narrowed part of the renal pelvis and ureteral junction. Under direct vision, the narrowed segment of the renal pelvis and ureteral junction is longitudinally incised through the full thickness of the lateral wall of the ureter with cold knife, electrocautery, or holmium laser instruments, until the fatty tissue is seen. A double-J stent is placed in the ureter for internal drainage for 3 to 8 weeks postoperatively. During ureterorenoscopy for pyeloplasty, endoscopic imaging can also be performed to determine the anatomical condition of the renal pelvis and ureteral junction, such as crossing of wandering vessels and high ureteral junction, to guide accurate incision and reduce the risk of injury to adjacent vessels.

　　(4) Balloon Dilation: This operation is often performed simultaneously with antegrade or retrograde endoscopic renal pelvis incision. A guide wire is inserted into the lumen through the percutaneous renal puncture approach or ureteroscope and left in place. Under X-ray guidance, a non-radioactive X-ray marked balloon catheter is inserted into the narrowed segment along the guide wire, the balloon is inflated with contrast medium, the narrowed segment is dilated, and maintained for about 3 minutes; the balloon catheter is removed, and a double J tube is placed routinely.

　　3. Postoperative Efficacy Judgment:Experiments show that the re-establishment of communication between smooth muscle cells after renal pelvis ureter anastomosis, that is, the reconstruction of cell bridges, can only be completed within 4 to 6 weeks after surgery. Therefore, the efficacy of renal pelvisoplasty should be evaluated at least 6 weeks after surgery to determine the success or failure of the operation. Generally speaking, after renal pelvisoplasty, the clinical symptoms of renal pelvis ureteral junction obstruction, such as lumbar swelling, abdominal pain, mass, fever, and others, disappear, which can be considered as cured. As for the postoperative imaging examination showing dilated renal pelvis and calyces that have not significantly decreased, it is mostly a normal phenomenon; after renal pelvisoplasty for chronic obstructive hydronephrosis, although the dilatation of renal pelvis and calyces has improved, it is difficult to completely disappear. Therefore, do not make conclusions prematurely, and do not blindly decide to take a second surgical treatment. In summary, it is necessary to judge further based on the changes in clinical symptoms and regular urinary tract造影 examinations or pressure-flow tests. If there are no symptoms such as lumbar swelling, abdominal pain, mass, fever, and repeated excretory urinary tract造影 examinations all show unobstructed drainage, and the dilatation of renal pelvis and calyces has not worsened, it can be confirmed as a successful operation. If necessary, diuretic renal imaging examination can be performed to determine the passage condition of the renal pelvis ureteral junction.

　　Secondly, Prognosis

　　Many researchers agree that early treatment is feasible and effective for restoring potential renal function, especially for children under one year old, where renal function damage is often less than 45%. If diagnosis is not made until adulthood, severe chronic obstruction often leads to progressive renal function damage. Poor drainage of urine and recurrent infections often form stones. Even in older patients, renal pelvisoplasty can be used to save the situation. Patients with poor renal function (10% to 25%) can also achieve partial recovery after surgery. A few patients with severe renal function damage may need nephrectomy.