(I) Definition
Acute urinary retention (AUR) is the acute onset of bladder distention and inability to urinate, often accompanied by pain and anxiety due to significant urge to urinate, which seriously affects the patient’s quality of life. The common causes of AUR include: general or regional anesthesia, excessive fluid intake, overfilling of the bladder, urinary tract infection, prostate inflammation, excessive alcohol consumption, use of sympathomimetic or anticholinergic drugs, etc. Spontaneous AUR often has no obvious trigger.
(II) Epidemiology
The incidence of AUR is significantly higher in men than in women, and can exceed that of women by more than 10 times. Among men, the incidence is high in older men, with 10% of older men aged 70-79 years having AUR within five years, 30% of older men aged 80-89 years having AUR within five years, and only 1.6% of men aged 40-49 years having AUR within five years. 65% of AUR is due to prostatic hyperplasia, and in the PLESS study, the incidence of AUR in those with prostatic hyperplasia was 18 /1000 person-years. AUR in women often has an underlying neurological component. AUR rarely occurs in children and is usually due to infection or surgical anesthesia.
(C) Etiology
1. Urethral obstructive factors: increased resistance to urinary flow due to mechanical obstruction (e.g. urethral stricture, blood clot or stone blockage) or dynamic obstruction (e.g. increased alpha-adrenergic activity, inflammation of the prostate).
2, neurogenic factors: bladder sensory or motor nerve damage (such as caused by pelvic surgery, multiple sclerosis, spinal cord injury, diabetes mellitus, etc.).
3, bladder myogenic factors: weak bladder contraction caused by overfilling of the bladder, etc. (such as anesthesia, excessive alcohol consumption).
(IV) Pathophysiology
The pathophysiological mechanism of AUR is still unclear, but it is now believed that the following factors are involved: prostate infarction, alpha-adrenergic activity, decreased prostate mesenchymal/epithelial ratio, neurotransmitter modulation and prostate inflammation.
The onset of acute urinary retention is sudden and painful as the patient’s bladder swells with urine but cannot be expelled. The causes of acute urinary retention mainly include obstructive, neurogenic and myogenic. Through detailed history questioning and physical examination, together with corresponding laboratory tests and auxiliary examinations, the causes and diagnosis can be clarified and provide a basis for subsequent treatment.
(I) Basic examination
l. Medical history inquiry (recommended)
(1) The presence of lower urinary tract symptoms and their characteristics, duration, and concomitant symptoms.
(2) History of surgery and trauma before the occurrence of acute urinary retention, especially history of trauma and surgery of lower abdomen, pelvis, perineum, rectum, urethra and spine; history of invasive examination and treatment such as transurethral catheterization, cystourethroscopy and urethral dilatation.
(3) Past history should also pay attention to: past urinary retention, overflow incontinence, hematuria, lower urinary tract infection, urethral stricture, urinary stones, urethral excretion properties such as stones, celiac clots, tissue masses, recent sexual intercourse, abdominal pain or bloating, constipation, blood in stool, shock, diabetes mellitus, neurological diseases, systemic symptoms and other medical history. Male patients should also be asked about any history of prostate enlargement and its International Prostate Symptom Score (IPSS) and Quality of Life Score (QOL), acute prostatitis, and encopresis. Female patients should also pay attention to the history of postpartum urinary retention, presence of pelvic inflammatory disease, pelvic compression diseases such as uterine fibroids and ovarian cysts, pelvic organ prolapse such as uterine prolapse, anterior or posterior vaginal wall prolapse, dysmenorrhea, hymenal atresia, vaginal discharge properties, etc.
(4) Ask for medication history to find out whether the patient is currently or recently taking drugs that affect the function of the bladder and its outlet. The common ones are muscle relaxants such as drugs used for anesthesia during surgery and flavonoid permethrin, M-blockers such as atropine, scopolamine, tolterodine, etc., and alpha agonists such as ephedrine and midodrine hydrochloride. Other drugs such as antidepressants, antihistamines, antipyretics, antiarrhythmics, antihypertensives, opioid analgesics, mercurial diuretics, etc. can also cause urinary retention.
2.Physical examination (recommended)
(1) General examination: including body temperature, pulse, respiration, blood pressure and other vital signs, paying attention to the mental status, development, nutritional status, gait, posture, and the presence of anemia or swelling.
(2) Local and genitourinary system examination.
Visual examination: except for particularly obese patients, overinflated bladder can mostly be seen in the suprapubic area; some patients can see overflow incontinence and narrowing of the external urethra; some can also see eczema, bleeding, hematoma or bruising, swelling, and surgical scars in and around the perineum, external genitalia, or urethral orifice. In addition, male patients can be seen with prepuce or foreskin impaction, narrow circumcision, and female patients can have pelvic organ prolapse, hymenal atresia, etc.
Palpation: A distended bladder can be palpated in the suprapubic region of the lower abdomen, and there is pain and a sense of urinary urgency with pressure, except for some neurogenic bladders. Long-term chronic posterior renal obstruction may lead to severe hydronephrosis of the diseased kidney, and an enlarged kidney may be palpated under the rib cage. Urethral stones or scars in the body of the penis may also be palpable. Urethral or vaginal masses may also be palpable. Other abdominal masses should be noted. For example, the nature of the lower abdominal and pelvic masses and their possible origin should be screened, such as giant bladder tumors, intestinal tumors, uterine fibroids, ovarian cysts, etc., and double palpation should be performed if necessary. Note the fecal masses.
Auscultation: A distended bladder sounds turbid on percussion in the suprapubic area and can sometimes distend to the level of the umbilicus. Mobile turbid sounds can determine the presence or absence of ascites and should be performed after emptying the bladder of urine.
(3) Rectal palpation: It is best performed after the bladder is emptied. Rectal palpation can understand the condition of anal sphincter tone, anal canal sensation, random contraction of pelvic muscles, etc., and the presence of tumors or fecal masses in the rectum. For male patients, it can also find out whether there is prostate hyperplasia, prostate cancer, prostate abscess, etc.
(4) Neurological examination: Urinary activity is regulated by the nervous system and involves central nerves above the brainstem, spinal cord centers, peripheral vegetative and trunk nerves, bladder and urethral nerve receptors and transmitters, etc. Therefore, a thorough neurological examination can help distinguish between combined neurogenic bladder and non-neurogenic bladder. Clinical examination of the plantar reflex, ankle reflex, testicular reflex, bulbocavernosus reflex, anal reflex, abdominal wall reflex, saddle area and lower extremity sensation, and lower extremity movement are often performed, with the assistance of a neurologist if necessary.
3.Urinary routine (recommended) Urinary routine can find out whether the patient has hematuria, pusuria, proteinuria and urine sugar, etc.
4.Ultrasound examination (recommended) Transabdominal ultrasound examination can find out whether there is fluid or dilatation in the urinary system, stones, occupying lesions, etc. In male patients, the shape and size of the prostate gland, the presence of abnormal echogenicity, and the degree of protrusion into the bladder can be found. It is also possible to understand other lesions outside the urinary system such as uterine fibroids and ovarian cysts. In addition, ultrasound residual urine volume determination is feasible after the patient’s acute urinary retention is relieved and he/she can urinate on his/her own.
(B) Depending on the results of the initial evaluation, some patients need further tests
1.Renal function (optional): Because bladder outlet obstruction can cause hydronephrosis, ureteral dilatation reflux, etc., which eventually leads to renal function impairment and elevated blood creatinine, it is recommended to choose this test when renal insufficiency is suspected.
2, blood glucose (optional): diabetic peripheral neuropathy can lead to diabetic bladder, blood glucose, especially fasting blood glucose test can help clarify the diagnosis of diabetes.
3. Blood electrolytes (optional): Hypokalemia and hyponatremia can also lead to urinary retention, so this test is recommended for those who suspect electrolyte disorders.
4. Serum PSA (optional): Prostate cancer, prostate hyperplasia, prostatitis may all elevate serum PSA. Acute urinary retention, indwelling catheterization, urinary tract infection, prostate puncture, rectal palpation and prostate massage can also affect the determination of serum PSA value.
5. Urinary diary (optional): After the acute urinary retention is relieved and the patient can urinate by himself, if the patient’s lower urinary tract symptoms are the main clinical manifestation, recording the urinary diary for 3 consecutive days can help to understand the patient’s urinary situation and is also helpful for nocturia identification.
The maximum urinary flow rate (Qmax) is the most important, but Qmax reduction cannot distinguish between obstruction and reduced contraction of the detrusor muscle, so it should be combined with other examinations and urodynamic examination if necessary.Qmax is more accurate when the urine volume is 150-200ml, and the examination can be repeated if necessary.
7.Urodynamic test (optional): This test is recommended when there is doubt about the cause of bladder outlet obstruction or when bladder function needs to be evaluated, combined with other relevant tests to exclude the possibility of neurological pathology or neurogenic bladder due to diabetes mellitus.
8. Urethrocystoscopy (optional): This test is recommended when urethral strictures, bladder urethral calculi, or intravesical occupational lesions are suspected.
9.Urethrography (optional): This test is recommended when urethral stricture is suspected.
10.Computerized tomography (CT) and magnetic resonance imaging (MRI) (optional) “CT or MRI is an important supplement when the nature of the lower abdomen or pelvic mass is not clear from ultrasound. When neurogenic bladder is suspected, CT or MRI is helpful to clarify central nervous system such as brain or spinal cord lesions.
(C) Not recommended tests: Intravenous urography (IVU) examination: mainly to understand the upper urinary tract, provides less information about the lower urinary tract such as the bladder urethra and is not recommended.
Treatment
(i)Emergency management
AUR requires emergency management and urinary drainage should be addressed immediately. Therefore, AUR due to other etiologies can be treated for different etiologies after urine drainage, except for those that can be released in the emergency, such as blockage of urethral stones or blood clots, stricture of the external urethra due to prepuce, and foreskin impaction.
AUR must be treated immediately by decompressing the bladder through placement of a catheter. emergency placement of AUR is done in a stepwise fashion, from smallest to largest trauma: indwelling Foley catheter, indwelling Coudé catheter, suprapubic cystostomy (SPC). Standard transurethral catheterization is easy to perform and is usually successful. If transurethral catheterization is unsuccessful or contraindicated, a stiff, angled elbow catheter (Coudé catheter) may be placed or a suprapubic cystostomy may be performed. If the Foley or Coudé catheter fails, other measures may be tried before deciding to perform a cystostomy, such as placement of a guide rod inside the catheter, urethral dilatation or urethral cystoscopy, or placement of a Foley catheter along the guide wire after a transurethral guide wire is left in place, which may allow successful placement of a Foley balloon catheter in some patients in whom conventional catheterization has failed. Hematuria, hypotension, and diuresis after decompression are potential complications of rapid bladder decompression, but there is no evidence that slow bladder decompression reduces these complications. The volume of urine drained during the first 10 to 15 minutes after tube placement should be accurately recorded in the patient’s medical record, as this helps to identify whether it is an AUR or an acute episode of chronic urinary retention, and helps to predict the success of subsequent attempts to remove the tube for voluntary voiding and the chance of needing surgical management.
In patients with urethral strictures secondary to AUR, a guidewire can be left in place under direct endoscopic view through the strictured segment of the urethra, followed by dilatation of the urethra with a dilator before placing a catheter along the guidewire. For acute bacterial prostatitis with AUR, suprapubic cystostomy is recommended to drain urine, and fine catheterization can also be used, but the catheter should not be left in place for more than 12 hours, and antibiotic treatment should be applied immediately.
1.Urethral catheterization
Patients with acute urinary retention caused by diseases such as urethral obstruction below the bladder or neurogenic bladder can have a catheter inserted through the urethra for bladder decompression. The procedure of catheterization should strictly follow the principle of asepsis.
The only absolute contraindication to catheterization is urethral injury, including confirmed or suspected urethral injury. Patients with severe pelvic trauma or pelvic fractures often have urethral injury, and if urethral injury is suspected, retrograde urethrography must be performed prior to catheter insertion. Relative contraindications to catheterization include: urethral strictures, recent urethral or bladder surgery, and patient resistance or non-cooperation.
A 16F or 18F catheter is available for most adult patients. Patients with urethral strictures may require a thinner catheter (12F or 14F), and some patients with prostatic hyperplasia may require a thicker catheter (20F to 24F) to avoid kinking of the catheter as it passes through the prostatic portion of the urethra, or a coudé catheter may be used. Patients with carnal hematuria should use a thicker catheter, which is inserted and then flushed to remove blood and blood clots from the bladder. A three-lumen catheter can be used for continuous bladder flushing to avoid clotting in the bladder.
Complications of catheterization: urinary tract infection (UTI) is common, and many patients present with only asymptomatic bacteriuria, but some patients may develop acute pyelonephritis, bacteremia, or even urinary sepsis. Patients who are elderly, diabetic, have renal insufficiency or advanced, life-threatening underlying disease are at increased risk for catheter-associated urinary tract infections. Prevention of catheter-associated urinary tract infections: strict aseptic intubation techniques, keeping the collection system as airtight as possible and shortening the duration of catheter retention. Routine antibiotics are not recommended for patients with emergency catheterization, and prophylactic antibiotics are only valuable for patients requiring intermediate indwelling catheterization; routine prophylactic use of antibiotics is not beneficial to patients and can lead to the proliferation of drug-resistant bacteria. However, antibiotic therapy may be considered for patients at high risk for infection and for patients undergoing certain invasive procedures (e.g., transurethral resection of the prostate and renal transplantation). Other complications of catheterization include foreskin impaction, urethral injury, and urethral stricture.
Patients with AUR can take the tube home after placement and wait for appropriate follow-up consultation, but admission is necessary for patients with renal insufficiency, urinary sepsis, other serious concurrent diseases, or difficult follow-up.
2. Suprapubic cystocentesis fistula
Indications for suprapubic cystocentesis fistula include patients with AUR who have contraindications to transurethral catheterization or failed transurethral intubation. Contraindications to suprapubic cystotomy include bladder emptiness, history of previous lower abdominal surgery with severe scar adhesions, and history of previous pelvic radiation therapy with severe scar adhesions, with significant systemic bleeding disorders being a relative contraindication.
Compared to transurethral catheterization, suprapubic cystostomy has a relatively low incidence of urinary tract infection and does not result in urethral stricture. Another advantage is that the tube can be clamped without the need to remove it to try to urinate, thus avoiding the need for reinsertion after failed urination. Suprapubic cystostomy is more comfortable and acceptable to the patient and is particularly suitable for patients who require preservation of sexual function. However, cystostomies have a relatively higher incidence of pain, hematuria, and poor catheter drainage. In patients requiring placement for more than 14 days, suprapubic puncture fistulas are less likely to cause discomfort, develop bacteriuria, or require re-catheterization than transurethral catheterization. However, some studies have reported a similar chance of complications (including asymptomatic bacteriuria, lower urinary tract infection, or urinary sepsis) with transurethral catheterization and suprapubic fistulas.
Suprapubic cystostomy is a more complex operation than catheterization, and possible complications include: hematuria, ureteral injury, large vessel injury, kinking of the fistula or blockage by blood clots, leakage around the fistula, infection or abscess formation, failure of the procedure, and serious complications such as bowel perforation, peritonitis, or even death. Carnal hematuria is common and is mostly transient. If the bladder cannot be palpated before puncture or if bladder filling is unsatisfactory, the use of ultrasound localization can help determine the location of the bladder and improve the safety of the puncture. If available, the new Seldinger
SPC puncture set, the cystostomy tube can be placed into the bladder along the guidewire, which is safer than the traditional blind puncture placement and can improve the success rate.
3.Puncture and urine extraction method (optional)
In order to temporarily relieve the patient’s pain when a catheter cannot be inserted and a puncture fistula is not available, a cystocentesis can be performed under aseptic conditions at the midline of the second finger on the superior border of the pubic symphysis to extract urine to temporarily relieve the patient’s symptoms and then transfer to a hospital with conditions for further treatment.
(ii) Etiological treatment
In addition to the causes that can be released in emergency, such as blockage of urethral stones or blood clots, narrowing of the external urethral opening due to prepuce, and foreskin impaction, AUR caused by other etiologies can be treated for different etiologies after urine drainage.
If the foreskin is embedded, the foreskin can be reset manually, and if the foreskin is circumcised, a dorsal circumcision is feasible. If the external urethral stenosis is atretched, an external urethrotomy is possible. For AUR caused by urethral calculi, direct transurethral stone extraction or lithotripsy is possible. For posterior urethral calculi, cystoscopy is feasible to push the stone back to the bladder, and the stone can be treated after the catheter is left in place. AUR caused by a blood clot in the bladder may require cystoscopic clearance of the clot followed by indwelling catheterization. If AUR is caused by constipation, laxative treatment is required along with placement of a tube to drain bladder urine. AUR after urethral trauma can be treated with urethral anastomosis or commissurotomy, or it can be preceded by suprapubic cystostomy. Postoperative AUR can be treated with neostigmine or acupuncture before catheterization.
1.Surgical treatment (optional)
Complications of long-term catheterization include urinary tract infection, sepsis, trauma, stones, urethral stricture or urethral erosion, prostatitis, and may induce squamous cell carcinoma.
Surgical removal of the etiology of the occurrence of AUR may prevent recurrence of AUR at all, as well as avoid long-term or repeat tube placement. Patients with a successful first TWOC who have a high PSA level, a large rectal exam prostate volume, and a high bladder residual urine volume after TWOC are prone to recurrent AUR, and early elective TURP (transurethral resection of the prostate) is recommended for these patients.
Those who undergo emergency prostate surgery after an episode of AUR (within days of the onset of AUR) have increased complication rates of infection, perioperative bleeding, increased transfusion rates, and ≤3-fold increased mortality. Patients with AUR are more likely to be unable to urinate after TURP compared to patients who undergo TURP for voiding symptoms alone. Therefore, patients with BPH presenting with AUR are recommended to undergo TWOC first after the application of alpha-blockers and postpone the procedure later, and emergency prostate surgery is not recommended.
2. Intermittent home-cleaning catheterization (CiSC) {optional)
For patients whose AUR etiology cannot be effectively treated, CISC is an alternative to long-term catheterization. In a comparative study of CISC with indwelling catheter (IDC), the chance of resuming voluntary voiding was higher in the CISC group than in the IDC group (56%:25%), and urinary tract infections occurred in 32%:75% of the CISC and IDC groups, respectively. The chance of urinary tract infection is lower in CISC than in IDC. The major advantages of CISC over IDC are the ease of living without an external device and the ability to maintain sexual activity, as well as its ability to allow patients to attempt to urinate on their own. CISC can be used as a short-term alternative to preserved catheterization to postpone surgery after the onset of AUR, and also for patients with urinary retention after prostatectomy due to bladder force weakness, especially for patients with neurogenic bladder.
3.Pharmacological treatment (optional)
In acute urinary retention, urinary drainage is preferred because of the urgency and pain felt, and pharmacotherapy is used only as an adjunct to urinary drainage or when the patient refuses catheterization or is not suitable for catheterization. According to the mechanism of occurrence of acute urinary retention, the drugs that can be used to treat urinary retention at present mainly include parasympathomimetic drugs that enhance the contraction of the bladder forced urinary muscle and alpha-blocker drugs that relax the urethral sphincter.
1α-blockers: α-blockers can relax smooth muscle in the prostate and bladder neck and other areas, and relieve urethral obstruction due to synergistic dysregulation of the detrusor muscle or spasm of the detrusor muscle, and are mainly used to shorten the duration of catheter retention after acute urinary retention and to avoid recurrence of acute urinary retention. The first-line drug recommended is alfuzosin extended-release tablets (alfuzosin). In patients with BPH secondary to AUR with indwelling catheters, alfuzosin 10 mg once a day significantly improves the likelihood of resuming urination after 2 to 3 days of catheter removal and prevents recurrence of acute urinary retention after catheter removal, reducing the patient’s dependence on catheters.
Other similar recommended medications include doxazosin (doxazosin) and tamsulosin (tamsulosin). Adverse effects such as vertigo, postural hypotension, nausea and vomiting should be noted during use. Phenoxybenzamine can be used for acute urinary retention due to post-anesthesia or postpartum, as well as for acute urinary retention due to prostatic hyperplasia and hyporeflexia of the detrusor muscle. A small sample reported that terazosin and phenazepam may release urethral dilator muscle spasm after oral administration, allowing some patients with AUR to resume normal urination without the need for indwelling catheters.
2 Proposed parasympathetic ganglion drugs: acting on the cholinergic nerves of the bladder pushing muscle, can be used for acute urinary retention after surgery or in the postpartum period, mainly adapted to non-obstructive acute urinary retention, neurogenic and non-neurogenic pushing muscle contraction weakness, etc. Such drugs include: Uracholine, neostigmine, carbamoylcholine chloride, dipyridamole, etc. Uracholine, neostigmine and phenibut are more effective when used in combination. When these drugs are used intravenously or intramuscularly, attention should be paid to the possibility of cardiac arrest.
4.Other treatment measures
(1) open cologne: the main component of open cologne is glycerol (55%), triglyceride (45%-55%), magnesium sulfate (10%), glycerol can directly stimulate the rectal wall, through the nerve reflexes caused by defecation, and at the same time cause strong contraction of the bladder forced urinary muscle, sphincter relaxation, supplemented by the diaphragm and contraction of the rectus abdominis muscle, through this series of reflexes, so that the intra-abdominal pressure and bladder pressure increased, causing urination. The use of enemas with open syringes can relieve acute urinary retention in women after childbirth and in children, but it is not recommended for acute urinary retention due to prostatic hyperplasia.
(2) Acupuncture: Chinese medicine uses acupuncture to relieve acute urinary retention due to postpartum or postoperative anesthesia-induced weak contraction of the detrusor muscle. Acupuncture sites can be taken as Hegu, Sanyinjiao, and Feosanli, etc. Neostigmine acupoint injection can also be used for more obvious effect.
Trial removal of catheter (TWOC)
Long-term indwelling catheter may cause complications such as bacteriuria, fever, urinary sepsis, etc. Therefore, more and more patients try to remove catheter (TWOC), generally after 1 to 3 days of indwelling catheter TWOC, about 23-40% of patients can successfully urinate. TWOC in patients with prostatic hyperplasia can lead to postponement of surgery and sometimes may avoid surgery.
The length of time the catheter is retained correlates with the success of TWOC, and Djavan et al. divided patients with AUR into three groups: single catheterization to empty the bladder, retained catheterization for 2 days, and retained catheterization for 7 days. After extubation, 44%, 51%, and 62% of patients in the three groups successfully resumed spontaneous urination, respectively. Patients with bladder drainage of >1300 ml of urine at the time of tube placement benefited most from prolonged catheter retention, but the prolonged duration may increase the chance of UTI.
There is evidence that the application of alpha-blockers prior to TWOC increases the chance of successful voiding after extubation. A daily dose of 10 mg of alfuzosin for 2 to 3 days after retention of the catheter nearly doubled the success rate of TWOC, even in older patients (≥65 years) with bladder drainage of ≥1000 ml of urine at the time of placement. tamsulosin for 3 days after catheterization in patients with BPH also significantly improved the success rate of TWOC.
Even if the first TWOC is successful in patients with BPH, 50% of patients will have a recurrent AUR within a year and 35% will require surgical treatment within the following 6 months. Those with AUR without predisposing factors, large prostate volume, elevated serum PSA levels, short indwelling catheterization to TWOC, maximum urinary flow rate <5 ml/s, post-void residual urine volume (PVR) >500 ml, and poor response to alfuzosin therapy after the first AUR are at higher risk for recurrent AUR.
Recommendations
1, The emergency management of AUR can be done by indwelling catheterization or suprapubic cystocentesis. The use of ultrasound localization or Seldinger method cystocentesis can improve the safety of the operation.
2. Suprapubic cystocentesis is recommended for patients with AUR who require catheterization for more than 14 days. Suprapubic cystostomy is also recommended for drainage of urine in patients with acute bacterial prostatitis with AUR.
3. Antibiotics are not recommended routinely for patients with emergency catheterization, but may be considered for patients at high risk for infection and for patients undergoing certain invasive procedures (e.g. transurethral resection of the prostate and renal transplantation).
4. It is recommended that patients with AUR go home with a tube after placement and wait for appropriate follow-up consultation, but admission is necessary for patients with renal insufficiency, urinary sepsis, other serious concurrent diseases, or difficult follow-up.
5. It is recommended that patients with the first occurrence of AUR should have TWOC after 3 to 7 days of post-tubing application of alpha-blockers.
6, For patients with recurrent AUR, long-term retention of catheter or cystostomy tube is not recommended. If possible, surgical treatment should be taken to relieve the etiology of AUR, and treatment such as intermittent home-cleaning catheterization or prostatic urethral stent placement can be tried as appropriate.
7. For patients with BPH who develop AUR, immediate surgical treatment within a few days is not recommended. It is recommended that TWOC be applied first after the application of alpha-blockers, and then elective surgery later.
8. Parasympathomimetic drugs can be used for acute urinary retention after surgery or postpartum, and acupuncture and enema with open-loop have some therapeutic effect on relieving acute urinary retention caused by postpartum or postoperative anesthesia.