Schistosomiasis of the urinary and reproductive systems

　　3. Causes of Disease

　　2. The male Schistosoma haematobium is 10 to 15 mm long, with the widest part being 0.8 to 1 mm, and its body surface is covered with small nodules. There are 4 to 5 testes, located behind the ventral sucker, arranged in front and back, with the terminal end of the vas deferens dilated into a seminal vesicle. The two intestinal branches merge into a single blind tube at the middle of the body, extending to the end. The female worm is about 20 mm long, with the widest part being 0.25 mm, in a slender tubular shape, with both suckers being small, and only small nodules at the front and back ends of the body surface. The ovary is located behind the middle of the body, in an elongated oval shape; the positions of other reproductive organs are all as in Schistosoma japonicum; the uterus contains 20 to 30 eggs. The digestive tract is similar to that of the male. The eggs are 131 to 183 μm × 40 to 70 μm in size, with terminal spines. The eggshell is negative for acid-fast staining, while the eggshells of other schistosome eggs are positive for acid-fast staining. The adult worms are parasitic in the human bladder and pelvic venous plexus, and occasionally in the portal system. The female worm lays 200 to 500 eggs per day. The adult worms can survive in the human body for 3 to 6 years, with some living up to 30 years (average 3.4 years), and a pair of adult worms can produce between 250,000 and 600,000 eggs in a lifetime.

　　1. Schistosoma haematobium has two stages of reproduction, sexual and asexual, with the former occurring in the human body. After the female worm lays eggs, some are deposited in the human tissue and others are excreted outside the body. When the eggs encounter water outside the body, they quickly hatch into miracidia, which swim into the water and quickly find their specific intermediate host, snails. The miracidia then bore into the soft tissue of the snail and develop into mother sporocysts, daughter sporocysts, and cercariae. Each mother sporocyst can produce 20 to 40 or more daughter sporocysts, and each daughter sporocyst produces 200 to 400 cercariae. The time required for the miracidia to bore into the snail and the cercariae to escape is 5 to 6 weeks.

　　2、尾蚴从螺体逸出后，浮于水面寻找终宿主，遇到哺乳动物后，依其头部钻入皮肤角质，靠其尾部摆动及体部伸缩等作用，尾蚴于数秒至数分钟内钻进皮肤黏膜，并依其分泌物协助虫体进入毛细血管或淋巴管随后进入肺部，穿过肺毛细血管进入体循环，最后定居于膀胱及盆腔的静脉丛。埃及血吸虫及其他血吸虫都有其独自的寄居部位，其机制尚未阐明。1990年有作者报道，将不同种的血吸虫如间接血吸虫、梅氏血吸虫等在动物、螺中杂交可使成虫的产卵部位发生变化，尾蚴的逸出方法及生殖力等也有变化。

　　3、血吸虫虫卵对人体的致病作用明显，各种血吸虫致病部位不同，实验动物中证实，约20％的埃及血吸虫虫卵存在于中空器官，部分虫卵可从尿或粪便中排出，其余的虫卵或沉积于局部或随血流抵达肺、肝等处，并于局部小血管形成微小栓子，沉积于局部者则在宿主的肉芽组织反应中被破坏。其他虫卵则被钙化，并积聚于器官中，每条雌虫计算每天大概会形成90个至100个钙化的虫卵。

　　二、发病机制

　　大量虫卵沉积在膀胱及远段输尿管黏膜下及肌肉内，引起嗜酸性粒细胞性肉芽肿，很快膀胱黏膜增厚及发生溃疡。慢性感染时，整个膀胱受侵犯，纤维化及瘢痕形成。由于纤维组织收缩，膀胱容量变小，形成膀胱挛缩。输尿管口可因膀胱纤维化狭窄或扩张而失去活瓣作用，引起梗阻或尿反流，导致输尿管及肾积水。输尿管也可因虫卵沉积形成肉芽肿使输尿管狭窄，输尿管及膀胱周围可形成纤维脂肪瘤病（fibrolipoma），压迫输尿管加重输尿管梗阻。如继发细菌性感染可导致肾盂肾炎甚至脓肾，影响肾功能。约10％的患者由于梗阻及感染而发生肾、输尿管或膀胱结石。泌尿生殖道之间或尿路小肠之间可发生瘘管。

　　埃及血吸虫病也可累及前列腺、精囊、子宫颈、阴道、阴唇、卵巢或输卵管。虫卵也可沉积在盲肠、结肠、直肠、肝、肺、脑及脊髓等处引起病变。曾有报道由于血吸虫卵致淋巴管梗阻，导致外生殖器发生象皮肿。虫卵随血循环到达肺部，可引起肺部粟粒样肉芽肿。大量虫卵反复栓塞肺小动脉致慢性肺动脉高压及肺源性心脏病。虽然在流行区病人青春期以后虫卵排出减少，如果不治疗，病变仍可继续发展。膀胱因受累日久而癌变较常见。

　　The main complications of urogenital schistosomiasis include upper urinary tract obstruction caused by ureteral obstruction, infection, and stones, as well as bladder contraction and reproductive system lesions. Schistosome eggs can enter the brain and spinal cord through the blood circulation system, causing ectopic lesions, which may lead to serious neurological complications; eggs entering the lung through collateral circulation may cause pulmonary arteritis, even pulmonary heart disease.

　　One, Cutaneous leishmaniasis

　　The penetration of the tail sporozoite into the skin is often not noticed, but when a large number of tail sporozoites enter the human body at one time, skin allergic reactions may occur, such as itching, rash, or urticaria, which may last for several days.

　　Two, Invasion period or toxicosis period

　　It refers to the process of the larvae developing into adults, which takes about 2 weeks, with seasonal differences. If a large number of larvae arrive in the lungs at the same time, it may cause symptoms such as spastic cough, asthma, chest pain, etc. However, these symptoms are often mild and transient and may not be noticed. More common are prolonged high fever, reaching 38-40℃, accompanied by chills, sweating, headache, back pain, etc., lasting from several days to 3-4 months. Prolonged high fever may lead to symptoms such as lassitude, dull response, decreased appetite, weight loss, and anemia, indicating a serious condition. Physical examination: moderate enlargement of the liver and spleen, with possible tenderness.

　　Three, Symptom stage

　　The symptoms of the urogenital system during this period are due to the large number of eggs laid by the adult worms in the bladder, ureteral wall, and reproductive system. Initially, the eggs are surrounded by granulomas formed by a large number of eosinophils, macrophages, and tissue cells. The granulation tissue is gradually invaded by fibroblasts to form scars. Subsequently, the eggs die and calcify, causing serious lesions of the urogenital organs, such as ureteral stricture and bladder contraction.

　　1. Bladder lesions:Early symptoms are microscopic hematuria, gradually developing into urinary frequency, pain, urgency, suprapubic and lower back pain. The severity of hematuria varies, with typical terminal hematuria, and it may also occur throughout the urine. The bladder lesions can be divided into three stages:

　　(1) The first stage: Stress bladder, the bladder muscle is hypertrophied and easily stimulated to contract. Temporary compression of the wall segment of the ureter may occur, and the spastic contraction of the ureteral orifice may increase the pressure in the ureter and renal pelvis, causing non-calculus renal colic.

　　(2) The second stage: Bladder weakness, fibrosis of the bladder muscle fibers affects the contraction of the bladder. If the lesion continues to develop, the bladder wall becomes thin and expands, forming a posterior fossa of the trigone. If the neck of the bladder becomes narrowed due to fibrosis, it further increases the difficulty of urination. False diverticula may form in the bladder wall. When the detrusor muscle compensation is out of order, residual urine begins to be produced. Excessive residual urine may lead to false incontinence, and stones in the posterior fossa of the trigone.

　　(3) The third stage: Contractile bladder, due to fibrosis and scar formation of the bladder wall, the bladder gradually becomes smaller. At this time, urinary frequency and pain are加重, and when the neck of the bladder contracts severely, retrograde ejaculation may occur, and calcification may occur in the bladder, bladder neck, and ureter.

　　2. Ureteral lesions:The bladder wall segment of the ureter is most commonly affected, and it can also invade the lower segment of the ureter. The ureter can develop fibrosis, narrowing, and above the narrowing, the ureter can dilate, twist, reflux, and calcify. Fibroadenomatosis can occur around the bladder and ureter, compressing the ureter and aggravating the narrowing. Above the narrowing, the ureter and renal积水 can occur, and in schistosomiasis haematobium, 96% have vesicoureteral reflux, which further aggravates the ureteral and renal积水. The kidneys can form scars, atrophy, calcify, and stones can form. About 84% are complicated with bacterial infections, leading to pyelonephritis, and in severe cases, it can form purulent kidneys.

　　3. Urethral lesions:Blood-sucking schistosome nodules and ulcers can appear in the posterior urethra; the anterior urethra can become narrowed due to secondary infection, leading to urethritis, perineal cellulitis, perineal abscess, and fistula.

　　4. Lesions of the reproductive organs:Schistosome eggs can accumulate in the muscular layer of the seminal vesicle, causing the seminal vesicle to enlarge, form nodules, and harden. The lesions can extend to the mucosa of the vesicle wall, leading to hematospermia when ulcers occur. In the later stage, secondary infection, fibrosis, can lead to the seminal vesicle becoming smaller, atrophic, calcified, which can lead to infertility.

　　5. Schistosome eggs can also accumulate in the prostate:They are mostly located in the mucosa of the prostatic urethra, and schistosome nodules can also be found in the prostatic venous plexus. These nodules are often misdiagnosed as calculi, tuberculosis, or malignant changes. The symptoms are mostly lower back pain, perineal pain, and urethral pain. In the late stage, prostatic fibrosis can lead to decreased libido, premature ejaculation, and erectile dysfunction, which are easily misdiagnosed as chronic prostatitis. Prostatic biopsy is often needed for diagnosis.

　　6. Occasionally, granulomas caused by schistosomiasis occur in the epididymis and testis:Schistosomiasis haematobium is more common in adult women's external genitalia and lower vagina, and it can also be found in the cervix, uterus, ovaries, and fallopian tubes. The lesions are mostly ulcers and granulomas, with symptoms such as purulent leukorrhea, bleeding after sexual intercourse.

　　1. Snail control:In Africa, a combined measure of water conservancy construction and the use of snail-killing drugs is adopted. The density of the intermediate host snails decreases significantly due to death in the river during the dry season each year, but a few snails still survive in soil gaps or shaded places. After the dry season, they will breed again and become vectors of transmission, so snail-killing work must be carried out repeatedly.

　　2. Large-scale treatment:In Egypt, chemical treatment (praziquantel) targeting a large population was adopted, but it was not successful in eliminating the disease, mainly because it could not prevent re-infection. The 40mg/kg single-dose therapy of praziquantel is effective due to its good efficacy and few side effects, and it is effective for social control of the disease.

　　3. Improve environmental hygiene:If fecal management is strengthened and safe water use is ensured to prevent human-spirochete infections, it is not easy to achieve and is expensive.

　　The prevention and control strategies of this disease require long-term publicity and education for the residents in the epidemic areas. Humans are the only infectious source, and therefore, they are responsible for maintaining the life cycle of Schistosoma haematobium. Only on the basis of improving social and economic conditions and collective efforts can this disease be controlled and eliminated.

　　Urine microscopy may show red blood cells, white blood cells; 24-hour urine or terminal urine centrifugation, urine sediment can find schistosome eggs; sometimes eggshells can also be found by fecal sedimentation method.

　　1. Cystoscopy

　　The bladder capacity is reduced, and specific changes of schistosomiasis in the bladder mucosa can be seen. In the early stage, the eggs deposited under the bladder mucosa are scattered grayish-white granules like sand grains. The mucosa around the granules is congested, and each granule corresponds to a granuloma with the egg as the core. In the late stage, the eggs calcify into whitish color, and the bladder mucosa may also appear glassy or erythematous congestion, with ulcers that may be irregular in edge, pale in base, and congested around the mucosa. There may be tumor-like granulomas, which are round, pedunculated or sessile, red, and prone to bleeding, often occurring at the bladder base or trigone area. Due to long-term chronic irritation, the mucosa produces hyperplastic lesions, such as cystitis, glandular cystitis, multiple schistosomal polyps, and even malignant transformation. The neck of the bladder contracts and narrows, and the bladder mucosa may form trabeculae and pseudo-diverticula. Often accompanied by bladder calculi, the bladder mucosa thickens in the late stage, and the mucosa becomes polypoid. The orifice of the ureteral opening is very small, or it expands into a cave-like shape.

　　Biopsy can be taken through cystoscopy to confirm the diagnosis.

　　2. X-ray examination

　　On the KUB flat film, linear calcification of the bladder and ureter may be seen as a characteristic change of the disease. When the bladder is empty, it presents as unevenly wide transverse calcification lines; when the bladder is full, it presents as eggshell-like calcification. Ureteral calcification often coexists with bladder calcification and is more common in the lower ureter, sometimes extending to the entire ureter. The ureteral wall may show linear calcification, and spots or plaques of calcification may also be seen. Occasionally, there may be pelvicalyceal and calyceal calcification, often accompanied by urinary system calculi.

　　3. Intravenous urography

　　It often shows delayed renal imaging, hydronephrosis, tortuous ureters, dilatation, and even as thick as the small intestine. The ureteral wall segment or lower segment may be narrowed.

　　4. Cystography

　　When there are granulomatous or polypoid changes due to schistosomiasis, there may be varying sizes of nodular filling defects, bladder capacity reduction, and reflux phenomena in the ureters.

　　5. Ureterography

　　Visible urethral stricture or fistula.

　　1. Foods beneficial for urinary and reproductive system schistosomiasis

　　In terms of diet, pay attention to strengthening nutrition, eating more light foods such as vegetables and fruits, and supplementing necessary vitamins and trace elements, such as eating more cucumbers, bitter melon, and porophyllum.

　　2. Foods to avoid for urinary and reproductive system schistosomiasis

　　Try to avoid drinking strong alcohol, eating刺激性 foods, and avoiding fatty, fried, moldy, and salted foods.

　　1. Treatment

　　1. Drugs for killing Schistosoma haematobium

　　(1) Praziquantel: Effective against Schistosoma haematobium, Schistosoma japonicum, and Schistosoma mansoni. 40mg/kg, taken once, or in two divided doses.

　　(2) Nifurtimox: Effective against Schistosoma haematobium and Schistosoma mansoni. 0.25mg/kg, taken in two divided doses, for a course of 7 days. It is best to also take diazepam 2.5mg, three times a day, to alleviate adverse reactions.

　　(3) Methacrine: 150-200mg suppositories, 1 time/d, inserted 8-10cm into the rectum from the anus, lying in a head-down, buttocks-up position for half an hour, for 3 consecutive days.

　　2. Surgical Treatment of Complications

　　(1) Early ureteral wall stenosis: dilation through cystoscopy or incision of the ureteral orifice has poor long-term efficacy and often leads to recurrence of stenosis. Ureteroneocystostomy is recommended. If combined with lower ureteral stenosis, it can also be excised and anastomosed with a ureteral bladder flap.

　　(2) For long stenosis below the middle segment of one ureter, it is not recommended to perform anastomosis between the ureter and the contralateral ureter. Because schistosomiasis often affects both ureters, leading to bilateral stenosis in the long term, ileal replacement of the ureter is recommended. For bilateral stenosis below the middle segment, a segment of ileum can be used to make a 'Y' shaped anastomosis to replace both ureters.

　　(3) For atonic megacalyst, ureteral stenosis, ipsilateral pyonephrosis, or excretory urography showing ipsilateral renal dysfunction, initial nephrostomy drainage should be performed for a period of time, and further treatment should be considered after renal function recovery, rather than rushing to perform nephrectomy.

　　(4) In case of sudden anuria due to bilateral ureteral obstruction, emergency cystoscopy and ureteral catheter drainage should be performed. If catheterization fails, emergency nephrostomy should be performed.

　　(5) For contracted bladder neck, the contracted scar can be resected through the urethra.

　　(6) For contracted bladder, colonic augmentation cystoplasty or ileal cystoplasty can be considered.

　　(7) Radical cystectomy should be performed when bladder cancer occurs.

　　II. Prognosis

　　Most patients have mild infections with good prognosis, but the incidence and mortality rate of Schistosomiasis haematobium depend on the degree of infection. The mortality rate is 0% in Nigeria with a low incidence and few urinary tract obstructions, while the mortality rate could reach 10% in Egypt in the past when the infection rate was high. In severe cases and patients with non-functioning kidneys, the mortality rate could reach 50%. Patients could die of bilateral hydronephrosis with uremia. New effective drugs have improved the prognosis of Schistosomiasis haematobium, and active infections and polyp lesions in children can be quickly cured. The urinary tract obstruction caused by polyps can be completely relieved within 2 to 6 weeks after treatment.

　　Foreign corporate personnel and tourists often have single, small contact with infectious water. Even if they excrete a large amount of eggs, the patients' response to treatment is good.