Echinococcus granulosus normally cycles between the dog and the sheep, and occasionally between other animals. Man is infested in the same way as the sheep[md]by ingesting a dog's faeces. Hydatid disease is widespread in many countries; Turkana, a remote area of north-west Kenya has the highest prevalence, with about 8% of the population infected. Programmes to control hydatid infection have been among the most successful measures for the control of infectious disease.
If hydatid disease is endemic in your area, you may find hydatid cysts in a patient's liver (80%), spleen (7%) or the other parts of his abdomen (14%), or occasionally in his lungs, brain, or kidneys, or indeed almost anywhere. If he has a peripheral cyst, expect that he has at least one in his liver too. You will be able to operate on cysts in his abdomen, but not those in his brain or lungs.
If he is from an endemic area and has a tense, almost painless, long-standing (years), smooth, rubbery, mobile cyst in his upper right quadrant, with little fever or malaise, it is probably a hydatid cyst[md]it may be enormous, and he may have more than one.
A hydatid cyst usually contains several litres of water- clear highly antigenic fluid. Outside, there is a thin, tough, fibrous ectocyst, made of tissue provided by the patient. Inside this, and separated from it by an easy plane of cleavage, is a thick, yellowish, slimy, gelatinous endocyst, which the parasite forms, and which tends to split and curl up on itself when you cut it. Scolices, which are tiny, barely visible, white granules, and daughter cysts, like grapes or soap bubbles, float free in the fluid of the cyst. E. multilocularis, a similar parasite, produces an alveolar or honeycombed cyst.
A cyst in his liver may rupture into: (1) his bile-ducts and cause cholangitis, or (2) a serous cavity, where it may cause a hypersensitivity reaction, varying from urticaria to anaphylactic shock.
The diagnosis is often difficult, and the disease may be so rare that you forget it as a possibility. There is never any hurry to operate, so investigate him as fully as you can. Surgery is likely to be difficult, so try to refer him.
When you remove a hydatid cyst, do so in the plane between the tissues of host and parasite[md]leave the ectocyst, and don't try to remove the entire cyst intact, unless you can do this easily, as in the ovary or spleen. Instead: (1) Gain access to the cyst, and pack it off, so that if any infective hydatid fluid does escape, it will not contaminate his peritoneal cavity[md]a single millilitre can contain thousands of scolices. (2) Aspirate some of the fluid, and inject a chemical to kill the scolices. (3) When this has had time to act, aspirate as much remaining fluid as you can. (4) Scoop out the endocyst and the daughter cysts. (5) Close the cavity, so that it does not leave a sinus or a fistula.
If he is a child, the cyst will probably be monolocular, so that aspirating it will not be too difficult. But if he is an adult, it is likely to be multilocular, so that: (1) the fluid will be difficult to aspirate, because the daughter cysts block the needle, and (2) the scolices will be difficult to sterilize, because the scolicide cannot penetrate in to them.
The great dangers are that you will spill the fluid which may: (1) allow daughter cysts to establish themselves in his peritoneal cavity, and (2) cause anaphylactic shock. The recurrence rate is usually at least 25%.
The medical treatment of hydatid disease with albendazole (Smith, Kline and French) 10 mg/kg/day in two divided doses daily for 8 weeks appears promising at the time of writing.
Fig. 31-12 A HYDATID CYST OF THE LIVER. A, a high paramedian incision. B, the cyst exposed. C, the cyst packed off, a purse string suture inserted, and the cyst being aspirated. Some scolicide is then injected and left inside for 3 minutes. D, sucking out the rest of the fluid. E, removing the daughter cysts with a spoon. F, removing the endocyst with sponge forceps. G, swabbing out the cavity with scolicide. Partly after Rob C and Smith R, ''Operative surgery: Part 1: Adomen, Rectum and Anus', (2nd edn 1969), p.322. Butterworths, with kind permission.
HYDATID CYSTS PREVENTION. If yours is an endemic area do all you can to educate the local population, especially about washing their hands and regularly deworming their dogs.
X-RAYS. Take a chest film: the patient may also have cysts in his lungs. A cyst in his liver may raise the right lobe of his diaphragm. An old aborted cyst may leave a calcified shadow.
ULTRASONOGRAPHY is the best way of detecting hydatid cysts. A lamellated membrane, detachment of the membrane from the cyst wall, or the presence of daughter cysts confirms the diagnosis.
SPECIAL TESTS. 30% of patients have an absolute eosinophilia. The Casoni test is negative in about 15% of cases. Other antibody tests, such as the ELISA test, also often give false negatives.
ASPIRATION. Many surgeons consider that you should not try to confirm the diagnosis by aspiration, because this may make the cyst leak, and may be fatal. Aspiration is safer if a cyst is superficial, and unlikely to leak into a serous cavity.
If you are aspirating what you think is an abscess, and you aspirate water-clear fluid, it is almost certainly a hydatid cyst. Continue aspirating to dryness, before you remove the needle. It will then be less likely to leak.
If you decide to aspirate the cyst in a patient's liver, do so under anaesthesia, so that it can be kept still for a few seconds, while you insert the needle.
CAUTION ! Don't try to tap a hydatid cyst merely to make it smaller.
DIFFERENTIAL DIAGNOSIS. Febrile? Ill? (hepatoma or amoebic abscess). Fever and a tender mass? (amoebic abscess). Liver diffusely enlarged and very tender? (amoebic hepatitis). Mass hard and nodular with loss of weight? (hepatoma). Craggy, irregular knobbly liver? (secondaries). A history of anything less than years, suggests that the mass is not a hydatid.
TREATMENT BY INJECTING A SCOLICIDE is sometimes possible. If he has a large single cyst, withdraw as much fluid as you can, and inject 1 ml of cetrimide. If he has any pain, abandon the procedure. If, not inject 5 ml of cetrimide. The great danger with this method is that if the needle is wrongly placed the cetrimide may enter his circulation. It can however be very effective, and the cyst may subsequently disappear.
CAUTION ! Don't use formalin for this purpose.
LAPAROTOMY [s7]FOR HYDATID CYSTS OF THE LIVER PREOPERATIVELY, to kill the hydatids and make dissemination less likely, give him a course of albendazole 10 mg/kg/day in two divided doses daily, if possible for 8 weeks. Also give him hydrocortisone 100 mg 12 and 24 hours before the operation, so as to minimize the danger of anaphylaxis when you open the cyst.
ANAESTHESIA. Give him a general anaesthetic and intubate him. He is at increased risk from laryngeal spasm
EQUIPMENT. An aspirator, or a large-bore syringe with a needle and 3-way tap. A long pair of sponge forceps, and a sterile kitchen spoon to scoop out the cyst. Coloured packs which will let you to see the brood capsules and scolices more easily. Soak the packs in scolicide. Two suckers, one for the trocar (if you use one), and one ready for any spills.
A scolicide, preferably cetrimide 40% concentrate (''Cetavlon'), which is safer than other scolicides which include 1% formalin in 0.9% saline, 10% sodium chloride, 70% alcohol, 0.5% silver nitrate, or hypochlorite.
CAUTION ! Higher concentrations of scolicides, particularly 10% formalin, are dangerous.
INCISION. This depends on where the cyst is.
If the cyst is high on the right, under his diaphragm, it may need a thoraco-abdominal incision, extrapleural dissection, and incision of his diaphragm. Refer him.
For cysts of the left lobe and most cysts of the right lobe, make a median or paramedian incision. If necessary, extend this laterally, so that you have adequate exposure. Another way of getting better access is to stuff packs, soaked with scolicide, into his right subphrenic space, so as to push his liver down.
The cysts present as smooth white swellings. Look and feel carefully to find how many he has. The rest of his liver is usually large, smooth, and distended.
Select a place where the cyst is close to the surface, and isolate it with carefully placed scolicide-soaked packs.
Aspirate at least half the fluid with a 1.5 mm needle, or a trocar attached to a sucker. If you withdraw watery fluid, it can only be a hydatid cyst. When the needle blocks, clear it by injecting a little scolicide. If needle aspiration does not work, use a trocar and cannula. If necessary, try introducing a multiholed catheter through the cannula. This will however increase the risk of spillage. If many daughter cysts block the sucker, it is probably multilocular.
Collect the fluid in a bowl containing an excess of scolicide. Keep a record of the volume you withdraw, as a guide to how much scolicide you will need to inject.
Fill a 50 or 100 ml syringe with scolicide, and inject it through the needle that you have used for aspiration. Go on injecting until the cyst becomes tense. Insert a purse string suture round the puncture site, and tie it snugly before you remove the needle. Wait for 3 minutes for the contents of the cyst to become sterile.
Aspirate some of the contents of the cyst, then open it through the part which presents most easily. Insert the tip of the sucker, and suck out as much of the remaining fluid as you can. You may remove up to 40 litres. Using a kitchen spoon, remove all the daughter cysts, sediment and debris. Then, using finger dissection, find the natural plane of cleavage between the ecto- and the endocyst. To get adequate exposure, you may have to incise the cyst across the full width of its bulge, and unroof it. Remove the yellow laminated membrane of the endocyst completely, piece by piece, with sponge forceps. There will be little bleeding.
CAUTION! (1) Try not to rupture the daughter cysts as you remove them, because their contents are probably still infective. (2) Don't try to remove the ectocyst; it is tightly stuck to the liver, and will bleed.
Swab the inside of the cyst with packs soaked in silver nitrate solution, and explore it for secondary cavities. If you find any, aspirate them and fill them with scolicide as above.
If the cavity is small, you may be able to bring its edges together together with mattress sutures.
If the cavity is large, you can: (1) Suture any obvious small bile duct openings, and leave it alone, which is probably the wisest method. (2) Fill it with ordinary 0.9% saline, and suture it. (3) Saucerize it by excising the protruding portion. The difficulty with this is that the cut surfaces of the liver will bleed. (4) Fill it with a graft of omentum. Dissect a strip of omentum on a vascular pedicle and stitch this into the cavity. The omentum will swell to fill the space and absorb the fluid from the cavity. (5) Stitch its edges to the surface of a separate skin incision (marsupialization). This is an old method, but it may be useful if he is very ill. (6) Stitch the walls of the cyst together with multiple catgut sutures, so that the cavity is obliterated.
Drain large cavities for about 10 days, especially if you have not been able to remove all the endocyst.
CAUTION ! (1) Don't let the cyst fluid spill, or daughter cysts will form in his peritoneal cavity. (2) If the needle hole does tend to leak, insert a purse string suture. (2) Don't try to excise the cyst in toto, or it will bleed disastrously.
DIFFICULTIES [s7]WITH HYDATID CYSTS If he presents with GENERALIZED ABDOMINAL SWELLING, consider the possibility of HYDATIDOSIS OF THE PERITONEAL CAVITY. At operation you may find his peritoneal cavity distended with hydatid cysts, and remove 2 bucketfuls of them. The surface of his gut may be seeded with small white nodules.
If he has a CYST IN HIS OMENTUM, try to remove it entire, with part of the omentum. If you cannot do this, aspirate and inject scolicide, as for the liver.
If he has a hydatid CYST OF HIS SPLEEN, do a splenectomy. In other sites excise it if you can, or evacuate it as in the liver. Don't sacrifice a kidney, just because it contains a cyst.
If his BLOOD PRESSURE FALLS alarmingly and there is no other reason for it, he is probably in anaphylactic shock (see below).
If he has OBSTRUCTIVE JAUNDICE, perhaps with cholangitis, you will have to open and drain his common bile- duct, as in Section 13.4. Remove all hydatid sludge, debris, and daughter cysts from the duct, and irrigate it thoroughly. Drain his common bile-duct with a T-tube.
If a CYST IS LEAKING into his peripheral bile ducts, refer him. Treatment is difficult, and his life is not, for the moment, in danger. If you cannot refer him, sterilize, evacuate, and drain the cyst. An external biliary fistula may develop, which may improve his cholangitis.
If he develops the features of a LIVER ABSCESS[md]a swinging fever, anorexia, and increasing pain, suspect that a hydatid cyst has become infected. Open it, saucerize it, and drain it. Treat him as in Section 31.12. Infection will have destroyed the hydatids.
If he develops the signs of PERITONITIS with an anaphylactic response, shock, and dyspnoea, his cyst has ruptured into his peritoneal cavity. Give him intravenous hydrocortisone 500 to 1000 mg, subcutaneous adrenalin (1 ml of a 1/1000 solution), or an antihistamine.
If his PERITONEAL CAVITY IS BULGING WITH DAUGHTER CYSTS, try to remove as many of them as you can. Then flood it with liberal quantities of a scolicide. Aspirate this and then irrigate it with saline to wash out the remaining scolicide.
If a cyst is CALCIFIED and asymptomatic, leave it.
If he develops a FEVER postoperatively, the cyst cavity is probably infected.
If he has RECURRENT CYSTS, they will probably take about 3 years to develop, be multiple, and be in his abdominal cavity. Distinguish recurrent cysts from the manifestation of an unsuspected second cyst.
Fig. 31-13 ONCHOCERCAL NODULES AND ENCYSTED GUINEA WORMS. Both are easy to remove surgically. A, and B, encysted guinea worms are commonly found on the trunk, particularly over the inferior angle of the scapula and the crest of the ilium. C, onchocercal nodules are usually found over the iliac crests, trochanters, sacrum, knees, shoulders or head. Partly after Charles Bowesman, ''Surgery and Clinical Pathology in the Tropics'. E and S Livingstone, with kind permission.