Congenital Megacalculus

　　First, Etiology

　　1. The etiology currently has no unified view, and it may be due to hyperplasia of the ureteral muscle layer during embryonic development or an imbalance in the ratio between the muscle bundles and the primary fibers. There is stenosis near the lower end of the ureter near the bladder, and there is a sharp contrast between the stenotic segment and the dilated segment. In some cases, there are transverse mucosal folds or canvas-like valves in the lumen of the lower end of the ureter.

　　2. There is no anatomical stenosis in the distal non-peristaltic megacalculus, but there is proximal dilation without peristaltic function. Under the microscope, the muscular layer of the ureter is relatively thin, there is hyperplasia of the circular muscle, and some cases show a decrease in the number of intermuscular nerve cells.

　　Second, Pathogenesis

　　The pathogenesis of congenital megacystis has not been fully elucidated. According to histopathological research, most scholars believe that it may be related to the following points:

　　1. The absence of longitudinal muscle in the wall of the terminal ureter.

　　2. The proliferation of collagen fibers in the muscle layer of the ureteral end, causing a disorder in the ratio of muscle bundles to collagen fibers, and a disordered arrangement of the muscle layer.

　　3. Muscle thickening at the end of the ureter, mucosal or submucosal inflammation. Due to the combined effects of one or several factors, the peristaltic function of this segment of the ureter is weakened or disappeared, urine excretion is not smooth, the pressure in the proximal ureter increases, leading to ureteral dilation and renal积水.

　　1. Urinary tract infection (UTI) refers to the growth and reproduction of pathogens in the urinary tract, which invades the mucosa or tissue of the urinary tract, causing inflammation. It is the most common type of bacterial infection. Urinary tract infection is divided into upper urinary tract infection and lower urinary tract infection. Upper urinary tract infection refers to pyelonephritis, and lower urinary tract infection includes urethritis and cystitis. Pyelonephritis is further divided into acute pyelonephritis and chronic pyelonephritis, which are more common in women.

　　2. Calculus, solid masses formed in the lumen of a catheter or cavity organ (such as the kidney, ureter, gallbladder, or bladder) in the human or animal body.

　　Congenital megacystis has no specific clinical manifestations. Most patients present with lumbago and distension. Occasionally, patients may present with lumbar mass, hematuria, refractory urinary tract infection, or renal insufficiency.

　　Principles of medication

　　1. The use of antibiotics is a necessary means to ensure the success of surgery and to reduce the risk of renal infection, which is also to protect renal function. Therefore, it is advisable to use antibiotics with low nephrotoxicity and to carry out targeted treatment under the reference of drug sensitivity tests and renal function indicators.

　　2. Fresh blood should be used as much as possible during surgery, especially in patients with renal insufficiency. Kidney protection treatment is also very important.

　　When accompanied by urinary tract infection and calculus, urine examination may show red blood cells, white blood cells, and pathogenic bacteria.

　　The trigone and ureteral orifice in cystoscopy are generally normal, especially in adults. The insertion of a ureteral catheter can be done without difficulty. In early cases, the X-ray film of the ureteral catheter shows only the lower segment of the ureter in a spindle or spherical shape. After injecting contrast agent, the ureteral catheter is immediately removed to take an emptying film, and the phenomenon of contrast agent retention and delayed emptying can be seen.

　　1. In X-ray imaging, the phenomenon of contrast agent reflux to the kidney can be seen in the ureter.

　　According to X-ray urography, changes in the shape of the renal pelvis and renal parenchyma can be observed, thereby estimating the degree of damage.

　　2. Renal pelvis: The renal pelvis can undergo various changes from normal, with a flat cup mouth, irregular cup mouth, convex elevation, to spherical expansion, etc.

　　The renal parenchyma can show varying degrees of damage, ranging from normal thickness (usually over 2cm), to thickness between 1 to 2cm, to thinning (below 1cm in children, below 0.5cm in infants and young children).

　　2. CT and MRI: CT can see the whole ureteral dilation, which can have varying degrees of hydronephrosis, and the ureterovesical junction can be seen to be narrowed. MRI can see the full picture of the dilated ureter, the lower end is narrowed, and it can be accompanied by hydronephrosis.

　　3. Ultrasound: It can be seen that the ureter on the affected side is dilated, with or without obvious hydronephrosis.

　　The diet of congenital巨ureter patients should be light, easy to digest, with a high intake of vegetables and fruits, a reasonable diet, and attention to adequate nutrition. In addition, patients should also pay attention to avoiding spicy, greasy, and cold foods.

　　First, Treatment

　　The treatment of congenital巨ureter in adults depends on the degree of ureteral dilation and renal function damage.

　　1. For patients with mild ureteral dilation and no obvious hydronephrosis, follow-up observation can be performed. There are literature reports that about 40% of cases can choose conservative treatment.

　　2. If the ureteral dilation is obvious but the renal function damage is not severe, ureteral trimming and整形 after bladder reimplantation can be performed. During the operation, attention must be paid to the necessity of resecting the 1-2cm of the diseased distal ureter. During trimming, part of the lateral wall of the lower ureter should be partially resected, with a length equivalent to one-third of the total length of the ureter, but not more than one-half, to avoid ischemic necrosis. It is necessary to perform anti-reflux ureteral bladder reimplantation, and the seromuscular layer can be incised on the side wall of the bladder top to reach the mucosa, with a length of 3-4cm. The mucosa at the distal end can be incised to form a small opening for anastomosis with the ureteral mucosa, and the lower segment of the ureter can be embedded in the muscle layer and the seromuscular layer sutured.

　　3. For patients with severe renal hydronephrosis and severe renal function damage, nephroureterectomy should be performed. If infection is present, renal fistula drainage can be performed first, and then nephroureterectomy can be performed after the infection is controlled.

　　Postoperative Complications and Prevention: ①Ureteral Necrosis: Clinical manifestations include urinary fistula and incision infection. During the operation, attention should be paid to protecting the outer membrane blood vessels of the ureter, and the diameter of the sutured ureter should not be too small. In case of the above complications, drainage surgery can be performed to extend the removal time of the stent tube, and temporary nephrostomy can be performed to divert urine if necessary. ②Ureteral Stricture: It can be caused by excessive trimming of the ureter, too small diameter after suture, or repeated urinary tract infection leading to fibrosis. During the operation, attention should be paid to the appropriate trimming of the ureter.