CHAPTER 8 COELOMIC DISORDERS 174 CHRISTINE L. DENSMORE Copyrighted COELOMIC DISTENSION Differential diagnosis: As dropsy is more accurately defined as a clinical presentation of disease rather than Dropsy a disease entity, the differential diagnoses are numer- Overview: Dropsy is a commonly applied term for ous, including not only the potential etiologies that lead coelomic (i.e., abdominal) distention due to ascites, or to free coelomic fluid accumulation but also other vari- the effusion and collection of fluid freely throughout ous causes of coelomic distension: neoplasia, organo- the coelomic cavity. It is a nonspecific syndrome and megaly, gastrointestinal obstruction, egg-binding. a clinical presentation, as opposed to a defined dis- Diagnosis: Diagnostic imaging may be useful in ease. Dropsy, or ascites, is generallyMaterial a sign of another determining if coelomic distention is related to fluid ongoing disease process, oftentimes one that is multi- accumulation or some other cause. If free coelomic systemic and impacting coelomic organs and tissues. fluid is suspected or observed, coeliocentesis and Etiology: Dropsy may be caused by a variety of evaluation of the coelomic fluid through cytology potential etiological agents, both infectious and non- and microbial (i.e., bacterial, viral and fungal) cul- infectious. Generally, dropsy is associated with infec- ture may often be diagnostically useful. tious disease processes associated with viral, mycotic - Management/control: Treatment and control or bacterial infection. In particular, pathogenic aero- optionsTaylor depend upon the underlying etiology. monad, pseudomonad and vibrio bacteria have all been associated with free serous fluid accumulation in Cichlid bloat, Malawi bloat the coelomic cavity among various species of fishes.1 Overview: Generally considered a disease syndrome Stressors such as rapid change in water temperature similar to dropsy, affecting specifically Malawi may predispose fish to bacterial diseases associated cichlids, a popularand group of ornamental fish among with dropsy.2 Rhabdovirus carpio, the causative agent of aquarium hobbyists. spring viremia of carp (SVC), is another of the more Etiology: Causative agents are varied and under- recognized causative agents associated with dropsy lying infectious diseases,Francis parasitism, and nutri- among some cyprinids and other fishes.3 Dropsy tional imbalances have been associated with cichlid associated with SVC has also been more specifically bloat.5,6 Among potential bacterial etiologies, both called “infectious dropsy.”4 Parasitism of the coelomic clostridiosis (Clostridium difficile) and francisellosis cavity or coelomic organs and infections of mixed eti- (Francisella noatunensis subsp. orientalis) have been ologies have also been associated with dropsy.2 reported in association with Malawi bloat.6,7 Clinical presentation: Clinically affected fish dis- Clinical presentation: Clinically affected fish may play coelomic distension of varying degrees of sever- display coelomic distension characterized internally ity (Figures 8.1 and 8.2). Severely affected scaled by ascites, hemorrhage into the coelomic cavity, fish may have protrusion of the scales that causes organomegaly and granulomatous inflammation of them to stand erect from the body surface, causing organs particularly the digestive tract.5,7 Additional lepidorthosis or a “pine cone” appearance (Figure signs may include anorexia, dyspnea, lethargic 8.3). Although dropsy is not unique to any taxo- behavior and mortality. nomic group of fishes, it is especially well recognized Differential diagnosis: Like dropsy, Cichlid or among pond cultured and hobbyist cyprinids. Malawi bloat is a clinical syndrome rather than a Coelomic Disorders 175 evaluation of the coelomic fluid through cytology and microbial culture may often be diagnostically useful. Management/control: Treatment and control options vary and depend upon determination of the underlying etiology. Salmonid water belly Overview: Water belly occurs among salt water pen- Copyrighted reared salmonid fish, including Atlantic salmon (Salmo salar), Chinook salmon (Oncorhynchus tshawyts- Figure 8.1 Severe coelomic distention in a female cha) and rainbow trout (Oncorhynchus mykiss). This tilapia (Oreochromis sp.) due to cystic ovaries. (Image condition is idiopathic and presents as marked coe- courtesy of S.A. Smith.) lomic distension related largely to the accumulation of seawater in the stomach (Figure 8.4). Although it may clinically resemble dropsy, the fluid accumula- tion occurs within the gastrointestinal tract and not free within the coelomic cavity. Material Etiology: The etiology has not been determined, although it is associated with dietary changes such as intensive feeding regimes and food composition, particularly related to fat and carbohydrates.8 Clinical presentation: Water belly has been reported Figure 8.2 Severe coelomic distention in a female to occur in sea-reared salmon and trout in both the madtom (Noturus sp.) due to cystic ovaries. (Image Pacific Northwest (United States and Canada) and courtesy of S. Boylan.) - Europe.Taylor9 Fish show severe distension of the coelomic cavity and mortality may also result. On necropsy, the stomach is fluid (seawater) filled, with stomach contents accounting for up to 40% of whole body 10 weight. Developmentand of this condition is likely to Francis Figure 8.3 Lepidorthosis (i.e., “pine-cone” appearance) in tilapia (Oreochromis sp.) due to coelomic distension. (Image courtesy of S.A. Smith.) specific disease. Differential diagnoses include the potential etiologies described for dropsy, as well as other various causes of coelomic distension that can impact Malawi cichlids, including neoplasia, organo- megaly and gastrointestinal obstruction. Diagnosis: Diagnostic imaging may be helpful in Figure 8.4 Coelomic distension in a captive salmonid determining if coelomic distention is related to fluid due to “water belly,” an idiopathic condition where there accumulation or some other cause. If free coelomic is an accumulation of sea water in the stomach. (Image fluid is suspected or observed, coeliocentesis and courtesy S. Boylan.) 176 CHAPTER 8 be chronic and as a result the stomach may be thin- other nonspecific clinical signs may present, such as walled and the liver may be atrophied. anorexia, lethargy, ataxia or abnormal swimming Differential diagnosis: Differentials include ascites behavior, and hyperpigmentation. (i.e., dropsy), organomegaly, neoplasia and gastroin- Differential diagnosis: Dropsy and peritonitis testinal obstruction. should also be considered in the differential diagno- Diagnosis: Gross external observation of marked sis list along with the potential underlying etiologies coelomic distension coupled with the signalment previously mentioned. (e.g., farmed salmonid) may provide a presumptive Diagnosis: Identification of the underlying cause is diagnosis.Copyrighted Verification that the coelomic distension potentially aided by imaging techniques such as radi- is related solely to an enlarged seawater-filled stom- ography, ultrasound, or computerized tomography, ach may be documented on necropsy. if available. Coeliocentesis to check for and evalu- Management/control: In some instances, dietary ate coelomic fluid content may help rule out dropsy changes such as reduction of the feeding rate have and its potential infectious etiologies. Exploratory been reported to improve this condition among surgery or laparoscopy for a nonlethal diagnosis of affected fish.11 an individual fish, or euthanasia and necropsy of an isolated specimen to evaluate disease within multi- Miscellaneous etiologies ple individuals or a population of fish may provide a (noneffusive) Material more definitive diagnosis. Overview: In addition to the accumulation of free Management/control: Management options are fluid within the coelomic cavity, many other factors dependent on the underlying etiology. affecting the size of coelomic organs or contents of the coelomic cavity may potentially result in appar- COELOMIC INFLAMMATION ent gross distension of the fish. Coelomic distension is a clinical sign of disease related to one or more - Steatitis coelomic organs or tissues, and further diagnosis is OverviewTaylor: Also known as “yellow fat disease,” steatitis usually required to identify the true underlying eti- is an inflammatory condition affecting adipose tissue. ology and appropriate management options. Usually, steatitis is described affecting coelomic adi- Etiology: Distension of the coelomic cavity that is pose stores that are associated with the mesentery and not related to effusion and/or accumulation of free sometimes associated with pancreatic tissue among fluid may be attributable to various underlying causes fishes. Still, the andcondition has been reported to affect such as organomegaly, overinflation of the swim other fat stores in fish as well, such as pericardial adi- bladder, egg retention in ripe females, parasitism, and pose tissue, fins or skin.12 The condition is most fre- neoplasia associated with coelomic tissues or organs. quently reported in culturedFrancis fish in association with Clinical presentation: Grossly apparent distention unsuitable diets, but may also occur in wild fish. of the body cavity may present to varying degrees. Etiology: Steatitis is generally nutritional in origin In subtle cases, comparing the body profile of an and commonly associated with lipid peroxidation. It individual fish to another presumably