Medicine is often like this, do not know or have not thought of something, the brain sometimes can not figure out, once clear, will feel that too much wrong way, the reason is actually very simple. I have a habit of recording my problems on paper in the past, but now it’s my iPhone and Mac. healing is the process of solving problems, not the process of accumulating them. Some problems need to be ambiguous, and some problems must be investigated deeply. For example, for leukemia patients, I may not need to know how to choose chemotherapy drugs, the specific course of treatment, but as a PICU doctor, must know the characteristics of the chemotherapy drugs used, toxic side effects, once the bone marrow suppression combined with sepsis or even septic shock, how to choose antibiotics, and so on. Pleural effusion is actually a very interesting type of disease in ICU, and pediatrics has special characteristics that distinguish it from adults. As an ICU physician, it is important to have a comprehensive understanding of pleural effusion. This is a case of pleural effusion from more than 1 year ago. There is no special record or imaging data, just write it down by feeling. 6-year-old boy with multiple injuries from a car accident (right lung contusion, closed abdominal injury? When he arrived at our hospital, his vital signs were still stable, the right pleural effusion was reduced compared with the previous one, and the closed drainage was smooth. On the next day, ultrasound indicated a traumatic diaphragmatic hernia on the right side and a partial protrusion of the right kidney into the thoracic cavity, while CT indicated a fracture of the pelvis. Due to repeated blockage of the drainage tube and poor drainage of the pleural fluid, he went to the operating room for thoracic surgery to reposition the thick tube and explore for no diaphragmatic breach. However, the pleural fluid was stubborn, the volume did not decrease, and the color gradually changed from bloody to dark yellow. After the orthopedic consultation, it was decided to perform external pelvic fixation, and postoperatively, a yellowish fluid was found to be slowly seeping from the right stent wound. At this time, after being reminded by the orthopedic director, it was thought that there was no other special problem, and after consulting the urology department, an enhanced CT of the abdomen was performed, and the giant urinary bladder in the chest and the right ureteral dissection could not be excluded. At this point, the cause of the persistent pleural fluid was understood. He was later transferred to urology and recovered well after surgery. It is no coincidence that 1 month after the incident, the emergency surgery was requested for consultation. A school-aged child with a large amount of right-sided pleural fluid after a car accident injury was not draining well, and when the consultation was held, the pleural fluid was urine-colored, also from a right-sided trauma. Urinothorax was considered at that time, and the surgery was not yet very convinced. After further consultation with urology, endoscopy was performed and right ureteral rupture was considered. After surgery, the pleural fluid was quickly absorbed. It is an interesting case that the focus was on intractable hemothorax, and we hoped that thoracic surgery would perform thoracoscopic exploration for active bleeding, without thinking about Urinothorax, and only later when orthopedic surgery revealed ooze, we associated it with Urinothorax. This also reflects the weakness of the diagnostic thinking about pleural effusion from the side. Here is a look at what happens to urine chest. Urothorax: often secondary to obstruction or injury of the urinary system for various reasons and the presence of perinephric collection of urine or leakage, through the diaphragmatic lymphatic channel into the thoracic cavity, resulting in the collection of urine in the thoracic cavity. Rare disease, often seen in obstructive urological diseases. Pleural fluid resembles urine and smells like urine. It is characterized by a leaky fluid with low pH, often <7.3. pH depends on urine pH. low total cell count, mononuclear cells predominate. Urothorax is divided into two categories according to the pathogenesis: obstructive urothorax and traumatic urothorax. 1. obstructive urothorax is associated with bilateral or terminal urinary tract obstructive disease, including prostate disease, right pelvic effusion with possible left renal vein obstruction, bladder cancer or metastatic bladder cancer, urethral valves, urethral perforation, and compression of the urethra by the pregnant uterus; 2. traumatic urothorax is associated with definite trauma (usually of medical origin). Etiologies include: surgical injury , blunt trauma, percutaneous pyelogram, renal biopsy, unsuccessful uretero-cystotomy, acute urinary tract obstruction secondary to renal stone with pelvic effusion, renal stone lithotripsy, and renal transplantation. Traditionally, it is believed that urine may reach the chest cavity by two routes: lymphatic drainage and leakage into the chest cavity through a ruptured urinary tract. 3. In addition to this, we should consider the case of abdominal fluid passing through defects in the diaphragm directly into the thoracic cavity. These defects can be clearly seen by thoracoscopy and this may be the main reason for the development of pleural effusion in patients with pneumoperitoneum. This may also be the causative factor in patients with urothorax who have a rapidly growing pleural effusion. Closed trauma is the main cause of pediatric ureteral injury, and limited national data show that almost all pediatric ureteral injuries are due to trauma. Therefore, it is important to be alert for the presence of this disease in children with violent abdominal trauma. Ureteral rupture complicated by urinary pleural fluid almost always occurs in childhood. The reason for this is that the posterior peritoneal tissue of children is slender, weak and loose, and the ureteral junction of the renal pelvis is fixed and easy to rupture, so when urine leaks out in large quantities, it can enter the thoracic cavity retrogradely along the retroperitoneal space and form urinary pleural fluid. In the present case, urinary extravasation was also found only during external pelvic fixation, and only then was the urinary pleural cavity associated. Gunner et al. reported 3 8 cases of intrapleural urine collection, often secondary to urinary leakage due to obstruction and or injury of different causes in the urinary system, and this intra- or extraperitoneal collection of urine enters the pleural cavity via the diaphragmatic channel and appears as an ipsilateral or bilateral pleural effusion. Features: (1) Triggering factors: trauma, urinary tract instrumentation, destructive urinary tract disease, external pressure or stone obstruction can cause retroperitoneal urinary cysts and cause uropleural chest. (2) Mostly unilateral (affected side); variable amount of pleural fluid, urine smell, leakage or exudate; (3) No clinical symptoms other than pleural fluid manifestation. (4) Creatinine, urea nitrogen and glucose concentrations in pleural fluid are significantly higher compared with serum concentrations. Pleural fluid creatinine/serum creatinine >1 has diagnostic significance; however, some patients have similar levels of urea nitrogen in pleural fluid compared with serum, and nephrogram imaging helps in diagnosis. (5) The pleura is intact, and once the obstruction is removed, the pleural fluid can be gradually absorbed, leaving no effect on the pleura. (6) Treatment is mainly to relieve urinary tract obstruction. The vast majority of diagnoses of urothorax are based on pleural effusion with urinary tract obstructive disease, and the pleural effusion disappears after the urinary tract obstruction is removed. Pleural effusions are judged to be leaking by Light’s criteria, but it should be noted that some urothoracic effusions have a marked increase in LDH, thereby misclassifying the urothorax as exudative. In the available literature, the biochemical indicators that are diagnostic for urothorax are pH, glucose and pleural effusion/serum creatinine anhydride ratio, the most important of which is the pleural effusion/serum creatinine anhydride ratio. A pleural effusion/serum creatinine anhydride ratio greater than 1 is generally considered a biochemical criterion for the diagnosis of urothorax [mean 4, range (1.08-19.8)]. In most cases of urothorax, the pleural fluid/serum creatinine ratio is >10. BUN and Glu in the pleural fluid are also elevated, but the pleural fluid/serum ratio is not diagnostic. It is not difficult to diagnose urothorax and awareness of this is key. However, the presence of this disease should be suspected in patients with pleural effusion with concomitant urinary tract obstruction or other diseases associated with it. Intravenous indocyanine, intravenous pyelogram or retrograde pyelogram, and technetium-99m-labeled DTPA renal perfusion scan are also feasible for patients suspected of having a renal pleural fistula to confirm the diagnosis. Treatment: Management of the primary disease, primarily by relieving urinary tract obstruction.