Hydatidosis is a disease that occurs frequently in certain areas and results from the presence of larvae of Echinococcus Granulosus. Renal involvement is rare, affecting less than 5% of verified cases. Typically asymptomatic for an extended period, renal hydatid cysts only manifest complications before they are diagnosed.

There is suspicion based on epidemiological, clinical, radiological and biological information.

Clinical presentations can vary, but hydaturia is a pathognomonic feature that appears in 10 to 30% of cases. The improvement of diagnostic accuracy has played a role in this regard.

Utilization of ultrasonography is common and both computed tomography and magnetic resonance imaging are useful in verifying the diagnosis. Surgery primarily serves as the basis for treatment.

The current standard procedure for preserving the kidney involves removing only the prominent dome through resection. In cases where renal destruction has occurred, total nephrectomy may be necessary. Percutaneous management techniques involving puncture, aspiration, injection and reaspiration should only be considered in highly selective instances. Nevertheless, the efficacy of this technique is still a topic of debate.

• Hydatidosis; Echinococcus Granulosus; Renal involvement; Kidney

Maachi Y, Babty M, Zerda I, Slaoui A, Karmouni T, et al. (2024) Hydatid Cyst of the Kidney, Literature Review. J Urol Res 11(2): 1150

Hydatidosis, caused by the larval form of Echinococcus granulosus in dogs and affecting humans, is present throughout North Africa as an anthropozoonotic disease.

Hydatidosis is a significant public health concern in countries bordering the Mediterranean basin, as well as New Zealand, Australia, Asia and America. The prevalence of E. granulosus correlates with economic and cultural factors which results in varying levels of hydatidosis across regions. Kenya falls under this category too [1,2].

At a rate of 200 per 100,000 inhabitants per year, hydatidosis has the highest prevalence. Within the Maghreb region lies an intermediate zone for this disease’s prevalence.

In Tunisia, the incidence of hydatidosis is 15 per 100,000 inhabitants annually while in Morocco it’s 8 per 1000,000 people every year [3,4]. Hydatidosis incidents are less frequent in Europe and mostly impact individuals migrating from endemic areas based on reports from [2,5-7].

Renal involvement is infrequent and represents less than 5% of visceral manifestations. The liver (60%) and lungs (30%), on the other hand, are more commonly affected as visceral sites.

The urogenital tract is most commonly affected by hydatid cysts in the kidneys (KHR).

Typically found in the cortex and with a preferred polar location, KHR is an almost always distinct primitive condition. While it predominantly affects the left kidney, the reason for this remains unknown. In rare cases (2-5%), KHR may be present alongside additional localizations such as hepatic or pulmonary involvement [2,4,8-12].

Parasitic cycle

Definitive hosts of E. granulosus are carnivores, including dogs, wolves and other canines in which this cestode is located within the small intestine.

The eggs exit the body through feces and are then consumed by herbivores, mostly sheep, who become an intermediate host. Upon hatching, hexacanth embryos emerge from the egg and penetrate the intestinal wall of their host before being carried to its liver via portal venous circulation in about 60-75% of cases or passing into its lungs via suprahepatic veins in around 15-30%. In rare instances, such as hematogenous or lymphatic route dissemination; these embryos may reach other organs besides those mentioned previously [3-5,10-13].

After a canine ingests a   hydatid   cyst,   larvae   (scolex) are released into the intestine. The scolex then undergoes transformation at this phase.

The infestation of adult worms in humans is caused by accidentally ingesting E. granulosus eggs, which can occur via consumption of contaminated food or contact with an infected dog or herbivore [3,10-11]. This condition is more prevalent in rural areas due to the greater likelihood of promiscuity with animals such as dogs and herbivores [10-12].

KHR does not have a specific clinical presentation.

The diagnosis of KHR is typically based on epidemiological, clinical, biological and radiological evidence. While it may not cause symptoms for many years in some cases, up to 10% are discovered incidentally [2-12]. Symptoms will vary depending on whether or not there has been rupture into the excretory tract [2,10-14].

Closed hydatid cyst

In 60-80% of cases, low back pain is the most common symptom while hematuria occurs in only 10%-30%. The reason for hematuria is caliceal fissuring caused by compression [2-7,9- 11,12].

As the cyst grows in size, it can cause compression. In 10- 40% of cases, a lumbo-abdominal mass is detected during clinical examination. It’s not uncommon to discover large masses as hydatid cysts typically develop unnoticed. Typically appearing as a smooth and firm movable mass with characteristics resembling that of a cystic lesion; such as regularity and renitency [2,3-9,11- 15].

In some cases, KHR has been linked to prolonged fever and very rarely (less than 3% of the time), arterial hypertension or digestive problems [9-12,15,16].

Ruptured hydatid cyst

Severe back pain is a common symptom of ruptured hydatid cysts. When daughter vesicles are released into the excretory tract, it can lead to full-blown renal colic. Hydaturia is often observed as a sign of urinary hydatidosis in 10-30% of cases [2,3,9-11,14,15-17].

Two imaging examinations, ultrasound and intravenous urography (IVU), allow diagnosis in over 70% of cases [2-11].

Ultrasound

Ultrasound has a 40-70% success rate in diagnosing KHR and can also identify other intraperitoneal areas [9,15-18]. Characteristics of hydatid cysts include the presence of liquid con-tents, parietal calcifications, and occasional membranous detachment or daughter vesicles [19].

Table 1 [20] indicates that Gharbi’s classification, which consists of five types for hepatic hydatid cysts, is also applicable to HRK.

Table 1: Ultrasound classification of hydatid cysts according to Gharbi et al.

The presence of type II is a clear indication for the existence of hydatid cysts [2,12-21]. On the other hand, distinguishing Type I from serous cysts can be accomplished through identifying the thick membrane [2].

A diagnosis in an endemic region is indicated by Type V, yet there are other lesions that may present a similar appearance, like renal cancer or tuberculous renal cavern [17-22].

When the size of KHRs is under 2 cm, ultrasound has limited diagnostic value and it becomes difficult to differentiate between them and tumors [9].

A type IV KHR may appear like a renal tumor or abscess due to its pseudotumoral, heterogeneous, hyperechoic and well circumscribed characteristics [2-20]. However, the presence of peripheral daughter vesicles, an echogenic or anechogenic spiral, and the presence of other hydatid localizations point to the hydatid nature of the mass [6,17-23].

The absence of vascular flow intra- and perilesionally detected by echodoppler can offer further evidence for the identification of type IV KHR. This makes echodoppler a valuable tool in the diagnostic process [15].

Tomography computed or CT

In situations where there is uncertainty in diagnosis, computed tomography (CT) can be an effective tool, especially with type IV and type V HRK [10,11-15]. Research has shown that CT outperforms ultrasound when detecting calcifications and providing a more comprehensive assessment of cystic contents while also offering clarity about the relationship between the cyst and adjacent organs. Additionally, it is capable of identifying any communication bet-ween the cyst and excretory tract based on findings from various studies [5,11-13,15-24].

Characteristic CT findings are observed in HRK [28,29].

Although CT cannot always exclude cystic metastasis, renal abscess or specific cystic tumors, it can eliminate simple renal cysts and necrotic tumors [25].

Magnetic resonance imaging

Magnetic resonance imaging is a medical scanning technique that uses strong magnetic fields and radio waves to produce detailed images of internal body structures.

There is a lack of established evidence regarding the usefulness of magnetic resonance imaging (MRI) in determining HRK diagnosis [12].

On all spin-echo sequences, the cyst’s outline exhibits a subdued signal. In T1, the vesicular fluid displays hypo-signal while in T2 it demonstrates hyper-signal [5,24-30].

The signal of the parent cyst fluid consistently surpasses that of this particular signal, particularly noticeable on T2 sequences [31].

While useful in ruling out cystic tumors, MRI is unable to distinguish between certain types of KHR and amoebic abscesses or specific necrotic tumors [6-24].

Biological Test

Hyper-eosinophilia can be observed in 20-50% of instances, but the likelihood is more significant when there are cyst fissures [2,9-11,15].

In situations of uncertainty, sero-immunological reactions are utilized as a diagnostic tool. Among these reactions, the indirect hemagglutination test proves to be highly sensitive [2,9,10-12], with an accuracy rate of 70%. However, there may be instances where false positives occur.

It is possible that this is caused by cross-reactivity with other parasites, particularly bilharzia [32].

Arc 5 immunoelectrophoresis was found to have a sensitivity and specificity of 100% in one study, but since it only involved seven cases, the results require further validation. Consequently, serological tests for hydatidosis are being conducted less frequently due to their lack of dependability in practice. They should only be considered when there is uncertainty regarding diagnosis. A cystic formation, can be either univesicular or multivesicular; its wall is clearly defined and may exhibit minimal contrast. Daughter vesicles are commonly observed in multivesicular cysts and typically have a lower density than the parent cyst, resulting in a rosette-like appearance [5,13,17,24-26].

Medical treatment

Medical treatment alone proves inadequate for majority of authors. As a standalone therapy, antiparasitic agents have yielded unimpressive outcomes and their efficiency remains debatable [33,34].

337 patients with hydatid cysts in different locations were treated by Teggi [35]. using medical treatment exclusively. Radiological criteria was used to evaluate the effectiveness of this treatment. Mebendazole (Vermox®) led to degenerative changes in 50% of treated cysts, while albendazole (Zentel®) resulted in such changes for 80%. The lack of literature data has left no agreement on KHR’s medical treatment approach.

Surgical treatment

The primary treatment for KHR typically involves surgery, with emphasis on preserving as much functional renal tissue as possible. The preferred surgical approach is lumbotomy.

This technique enables a retroperitoneal approach to the cyst, reducing the possibility of peritoneal swelling [2,9,11,12]. However, employing a median approach is only appropriate if there are coexisting cases of peritoneal localization or in situations where both kidneys are affected as determined by certain teams [10,12-15].

To prevent the possibility of swarming, it is necessary to cover the surgical area with drapes that have been saturated in a scolicidal solution such as hypertonic serum, formalin solution, hydrogen peroxide or silver nitrate [10-12].

Resection of the protruding dome: It is followed by carefully dissecting the cyst from surrounding tissue before excising its protruding dome or performing a partial cysto- pericystectomy, as this is usually needed due to the challenging cleavage between the renal parenchyma and cyst. Various studies have corroborated that these steps are frequently taken [2,9- 12,15].

To avoid the risk of hydatid fluid entering the bloodstream or bursting, it is necessary to sterilize the cyst before proceeding. Once ten minutes have passed, all contents should be properly aspirated and then opened for further examination.

The removal of the endocyst, which consists of the hydatid membrane and daughter vesicles, is necessary [10-15]. It is important to check for a kystourinary fistula as it may be present in 15-30% cases. Treatment options depend on factors such as the size of communication opening and appearance of pericyst. If there’s only a small connection communicating with calyx then absorbable stitches can be used to close them up but larger ones require catheterization & external drainage until postoperative day 10 when drain would get removed [2,9,10-15]. JP-type ureteral stent might also need placement depending upon assessment done by doctors

The approach to dealing with the remaining cavity is determined by its surface area.

To minimize the likelihood of suppuration, one can undergo capsulorrhaphy or use fat or omentum padding. In either scenario, it is advisable to implement drainage techniques that involve keeping a redon in proximity with the cavity [2,10-12].

Total pericystectomy: When the pericyst becomes sclerotic or calcified, it shows an indication. Following the section of externalized pericyst, dissection is carried out through the avascular midplane of adventitia to get rid of any remaining sclerohyaline layer. Open calyces are tied up using absorbable suture materials.

Partial nephrectomy: For sizable cysts, Partial nephrectomy is advised as suggested by few writers [9,12-15].

Most teams deem partial nephrectomy unjustified [11].

Total nephrectomy: This is exclusively for kidneys that have been damaged by a significant HRK or in scenarios involving extensive suppuration [3,5,15,16-27]. Evacuating the cyst simplifies nephrectomy and confirms destruction of the renal parenchyma.

Complication: A urinary fistula is present in 2 to 7 percent of cases and typically results from an unnoticed or recurring cysto-urinary fistula. In roughly half of instances, it progresses naturally resulting in drainage. If this isn’t the case, a ureteral stent should be placed for around eight to ten days [9-11,15].

The drainage of the remaining cavity. Some studies report rates of up to 8% for suppuration after surgery, which is typically managed by draining any persistent cavities. Rewritten without medical terminology: After some surgeries, an infection may develop in areas that were not completely treated. Up to 8% of patients experience this complication, but it can be resolved by removing any leftover material or fluid through a small incision made at the site. If the drain is not removed right after surgery, it should be maintained for several weeks. If maintenance does not work, surgical drainage becomes necessary [10].

Recurring incidents are very rare, and those that have been documented are considered exceptional recurrences.

Percutaneous puncture-aspiration and injection- reaspiration (PAIR): For a long time, percutaneous aspiration of hydatid cysts has been prohibited based on the potential danger of swarming and anaphylactic shock [17-38]. Nevertheless, various studies conducted since the 1980s indicate that puncturing a hydatid cyst for diagnostic reasons does not result in any significant adverse effects [17,39,40].

Between 1983 and 1993, Kohlhaufi [41], reviewed a number of European series containing a total of 104 cases in which hydatid cysts were treated via percutaneous drainage aided by ultrasound guidance. This analysis constitutes a meta-review.

Based on the literature review, there were no instances of severe complications among patients.

Under the guidance of ultrasound and local anesthesia, a Chiba or Seldinger needle can puncture Type I or II HRK [40-42].

Transparenchymal pathway is employed to drain hydatid cysts. Safest technique to prevent swarming is using a transparenchymal approach. Once the puncture has been made, it’s advised to aspirate fifty percent of the cyst volume.

The cyst is flushed with either silver nitrate or 20% hypertonic saline for a duration of 10 to 25 minutes.

The contents are aspirated again until a clear distinction between the endocyst and pericyst is visible [17,40-42].

If the HRK exceeds 6 cm, drainage will be maintained while a sclerosing agent (95% alcohol) is administered for a duration of 20 minutes at the end of the day.

After percutaneous treatment, patients are given oral medication with mebendazole or albendazole starting one week before the procedure and continuing for several weeks thereafter. Additionally, drainage is eliminated during this time.

Therapeutic indications: In most cases, authors opt for reference treatment involving the removal of the protruding dome to manage KHR. This approach has demonstrated effectiveness across all types of this condition. However, there is ongoing debate about the use of medical treatment in conjunction with resection as it does not seem to decrease recurrence rates [2,9-12,15].

Percutaneous treatment is being suggested by certain teams as a fresh alternative for treating KHR of types I and

1. Nevertheless, percutaneous methods are not efficacious in

managing other forms of KHR.

Medical treatment is systematically combined with percutaneous treatment when it is selected [40-42].

Medical intervention is only utilized in conjunction with surgery under two circumstances - systematically alongside percutaneous procedures [3,11,17,18,27,35-37].

Therapeutic abstention: Due to the risks associated with HRK’s evolution, it is crucial that this remains an exception rather than a rule. KHR has two potential evolutionary paths.

The volume of the KHR typically increases, causing it to push against calcific cavities and stretch their walls. This can lead to a higher chance (around 40%) of rupture into the excretory tract, which often results in superinfection. The cyst may eventually cause kidney destruction   through   mechanical   compression or obstruction of the excretory tract. However, there are rare instances where KHR devolves into involution and calcification [2-16].

Therapeutic abstention is only considered suitable for type V KHR if it is completely calcified and the serology results are negative. Regular monitoring, at intervals of approximately every six months, should be implemented [10-16].

KHR is an uncommon condition that warrants suspicion when a cystic mass is discovered in patients from endemic areas. The indications of KHR can vary greatly, with only hydaturia being considered pathognomonic and even then it occurs infrequently. Surgical intervention stands as the primary treatment method through resection of the protruding dome utilizing standard techniques; percutaneous treatments have yet to display their efficacy for this particular ailment.

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