Echinococcosis: Classification

WHO-IWGE PNM classification for alveolar echinococcosis (AE).

P Hepatic localization of parasitic structures.
PX No evaluation possible
P0 No evidence of hepatic involvement
P1 Peripheral focus without involvement of proximal vessels or bile ducts
P2 Central focus involving proximal vessels or bile ducts of a liver lobe
P3 Central focus with involvement of hilar (“pulmonary pedicle”) bile ducts or vessels of both lobes of the liver and/or involvement of two hepatic veins
P4 Any focus with spread along the hilar vessels and inferior vena cava (body vein entering the right atrium from caudal) and bile ducts
N Extrahepatic (“outside the liver“) involvement of adjacent organs (diaphragm (diaphragm), lung, pleura (lung pleura), pericardium (pericardium), heart, stomach, duodenum (duodenum), kidney, adrenal gland, Peritoneum (peritoneum), retroperitoneum (“behind the abdominal cavity”), pancreas (pancreas), regional lymph nodes, ligaments, thoracic and abdominal wall with adjacent muscles, skin, and bone).
NX No evaluation possible
N0 No evidence of involvement of adjacent organs or tissues
N! Involvement of adjacent organs or tissues
M Distant metastases (lung, CNS, spleen, kidney, peritoneum, bone, orbit (eye socket), skin, muscle, non-regional lymph nodes)
MX No evaluation possible
M0 No evidence of distant metastases
M1 Distant metastases

Classification of cysts in cystic echinococcosis (CE).

Stage Description Activity Therapy
CL unilocular lesion active cysts Drug therapy

Note: In a superficially located cyst, drug therapy alone should not be used because of the increased risk of rupture due to thinning of the cyst wall.

CE1 Hydatidensand(“double-line-sign”)
  • PAIR (puncture, aspirate, inject, re-aspirate) + albendazole.
  • Therapy of choice: surgical resection for easily resectable and large cysts (> 5 cm) with multiple daughter cysts (see below surgical therapyMedicinal pretreatment (at least 24 h before surgery, a total of three months of therapy before, during and after surgery).
CE2 Rosette character
CE3 “water-lilly-sign”)daughter cysts Transitional formsInvolutional stage
CE4 Heterogeneous cyst contents without liquid components inactive cysts Primarily inactive cysts (diagnosed as such) or cysts converted to this stage by drug therapy (CE4 and CE5) do not require treatment.

Note: CE4 cysts have a potential for reactivation to CE3b cysts.

CE5 solid,calcified cyst
  • Primary liver cysts CL, CE 4, CE 5: observe and monitor (Wait and Watch).
  • Secondary echinococcosis (spread of daughter cysts outside the parent cyst): drug therapy with a benzimidazole.