The diagnosis of eating disorders can be problematic in that a number of physical disorders can underpin the condition that will make a psychological approach inappropriate so it is important that psychologists ensure that all potential clients have been physically screened by a qualified physician to exclude these factors

The initial diagnosis should be made by a competent medical professional."The medical history is the most powerful tool for diagnosing eating disorders"( American Family Physician).[1] There are many medical disorders that mimic eating disorders and comorbid psychiatric disorders. All organic causes should be ruled out prior to a diagnosis of an eating disorder or any other psychiatric disorder is made. According to an in depth study conducted by psychiatrist Richard Hall as published in The Archives of General Psychiatry:

Medical illness often presents with psychiatric symptoms.

It is difficult to distinguish physical disorders from functional psychiatric disorders on the basis of psychiatric symptoms alone.

Detailed physical examination and laboratory screening are indicated as a routine procedure in the initial evaluation of psychiatric patients.

Most patients are unaware of the medical illness that is causative of their psychiatric symptoms.

The conditions of patients with medically induced symptoms are often initially misdiagnosed as a functional psychosis.[2]

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A consultation with a reputable medical professional who specializes in eating disorders is an indispensable part of both the diagnostic process and treatment. A complete medical and psychosocial history should be provided and a rational and formulaic approach to the diagnosis should be used.
Neuroimaging using fMRI, MRI, PET and SPECT scans have been used to detect cases in which a lesion, tumor or other organic condition has been either the sole causative or contributory factor in an eating disorder."Right frontal intracerebral lesions with their close relationship to the limbic system could be causative for eating disorders,we therefore recommend performing a cranial MRI in all patients with suspected eating disorders"(Trummer M et.al.2002)","intracranial pathology should also be considered however certain is the diagnosis of early-onset anorexia nervosa. Second, neuroimaging plays an important part in diagnosing early-onset anorexia nervosa, both from a clinical and a research prospective".(O'Brien et.al.2001).[3][4]

Without visible images of neuropathology, psychiatric disorders have been a fertile ground for stigma and bizarre propositions, as evidenced by etiologic theories involving “schizophrenogenic”[5] and “refrigerator mothers". Neuroimaging will clearly establish psychiatric disorders as being “medical”, thereby bringing these disorders into the mainstream in terms of public attitude and, perhaps more importantly, funding for treating these problems.(Derryck H Smith, MD, Canadian Psychiatric Association)
In addition to neuroimaging there are a variety of tests that may be performed to diagnosis and assess the effects of an eating disorder.

Medical Tests used in the Diagnosis and Assessment of Eating Disorders

urea nitrogen is the byproduct of protein metabolism first formed in the liver then removed from the body by the kidneys. The BUN test is used primarily to test kidney function. A low BUN level may indicate the effects of malnutrition.[20]

A BUN to creatinine ratio is used to predict various conditions. High BUN/creatinine ratio can occur in severe hydration, acute kidney failure, congestive heart failure, intestinal bleeding. A low BUN/creatinine can indicate a low protein diet, celiac diseaserhabdomyolysis, cirrhosis of the liver.[21][22][23]

tests the functioning of the parathyroid by measuring the amount of(PTH) in the blood. Test is used to diagnose parahypothyroidism. PTH also controls the levels of calcium and phosphorus in the blood (homeostasis).[30]

After ruling out organic causes and the initial diagnosis of an eating disorder being made by a medical professional a trained mental health professional aids in the assessment and treatment of the underlying psychological components of the eating disorder and any comorbid psychological conditions. The clinician conducts a clinical interview and may employ various psychometric tests. Some are general in nature while others were devised specifically for use in the assessment of eating disorders. Some of the general tests that may be used are the Hamilton Depression Rating Scale[38] and the Beck Depression Inventory.[39][40]

According to a recent report issued in The Journal of the American Medical Association (JAMA), anywhere from 40,000 to 80,000 deaths in the U.S. are attributable to misdiagnosis in the hospital setting per year. Also in the U.S., deaths due to medical errors are higher than the numbers attributable to the 8th-leading cause of death. More people die in a given year as a result of medical errors than from motor vehicle accidents (43,458), breast cancer (42,297), or AIDS (16,516).[41]

[42] These figures do not factor in those misdiagnosed outside the hospital setting or for individuals who present with psychiatric symptoms and receive contraindicated i.e. wrong, mental health care predicated upon poor diagnostic procedure. On average, 32,000 Americans commit suicide per year. 77% had seen a physician and 30% had received mental health counseling in the year prior. In England alone independent of the rest of the United Kingdom an average of four psychiatric patients die, many from suicide and another three suffer serious physical harm each day while under the care of the National Health Service.[43][44][45]

acute pandysautonomia is one form of an autonomic neuropathy, which are a collection of various syndromes and diseases which affect the autonomic neurons of the autonomic nervous system (ANS). Autonomic neuropathies may be the result of an inherited condition or they may be acquired due to various premorbid conditions such as diabetes and alcoholism, bacterial infection such as Lyme disease or a viral illness. Some of the symptoms of ANS which may be associated with an ED include nausea, dysphagia, constipation, pain in the salivary glands early saiety. It also affects peristalsis in the stomach. ANS may cause emotional instability and has been misdiagnosed as various psychiatric disorders including hysterical neurosis and anorexia nervosa.[46]

achalasia; There have been cases where achalasia, a disorder of the esophagus which affects peristalsis, has been misdiagnosed as various eating disorders including anorexia nervosa, bulimia nervosa, compulsive eating disorder and obesity related problems. It has been reported in cases where there is sub-clinical manifestation of anorexia nervosa and also in cases where the full diagnostic criteria AN has been met.[50]

superior mesenteric artery syndrome: (SMA) syndrome; "is a gastrointestinal disorder characterized by the compression of the third or transverse portion of the duodenum against the aorta by the superior mesenteric artery resulting in chronic partial, incomplete, acute or intermittent duodenal obstruction". It may occur as a complication of AN or as a differential diagnosis. There have been reported cases of a tentative diagnosis of AN, where upon treatment for SMA syndrome the patient is asymptomatic.[51][52]File:Borrelia burgdorferi (CDC-PHIL -6631) lores.jpg

Lyme Disease is known as the "great imitator", as it may present as a variety of psychiatric or neurologic disorders including anorexia nervosa. "A 12 year old boy with confirmed Lyme arthritis treated with oral antibiotics subsequently became depressed and anorectic. After being admitted to a psychiatric hospital with the diagnosis of anorexia nervosa, he was noted to have positive serologic tests for Borrelia burgdorferi. Treatment with a 14 day course of intravenous antibiotics led to a resolution of his depression and anorexia; this improvement was sustained on 3 year follow-up."[53][54]Serologic testing can be helpful but should not be the sole basis for diagnosis. The Centers for Disease Control (CDC) issued a cautionary statement (MMWR 54;125) regarding the use of several commercial tests. Clinical diagnostic criteria has been issued by the CDC (CDC, MMWR 1997; 46: 531-535).

Addison's Disease; is a disorder of the adrenal cortex which results in decreased hormonal production. Addison's disease, even in subclinical form may mimic many of the symptoms of anorexia nervosa.[55]

Simmond's disease (organic hypopituitarism) – "A 20-year-old Japanese man with a hypothalamic tumor which caused hypopituitarism and diabetes insipidus was mistakenly diagnosed as anorexia nervosa because of anorexia, weight loss, denial of being ill, changes in personality, and abnormal behavior resembling the clinical characteristics of anorexia nervosa"(Hotta, M. 1999)

Celiac Disease is an inflammatory disorder triggered by peptides from wheat and similar grains which cause an immune reaction in the small intestine."information on the role of the gastrointestinal system in causing or mimicking eating disorders is scarce."(Leffler DA et.al.)[56]

Gastric adenocarcinoma is one of the most common forms of cancer in the world. Complications due to this condition have been misdiagnosed as an eating disorder.[57]

helicobacter pylori is a bacteria which causes stomach ulcers and gastritis and has been shown to be a precipitating factor in the development of gastric carcinomas. It also has an affect on circulating levels of leptin and ghrelin, two hormones which help regulate appetite. Upon successful treatment of helicobacter pylori associated gastritis in pre-pubertal children they showed "significant increase in BMI, lean and fat mass along with a significant decrease in circulating ghrelin levels and an increase in leptin levels" (Pacifico, L)."SUMMARY: H. pylori has an influence on the release of gastric hormones and therefore plays a role in the regulation of body weight, hunger and satiety,"(Weigt J, Malfertheiner P).[58][59]

Gall bladder disease which may be caused by inflammation, infection, gallstones, obstruction of the gallbladder or torsion of the gall bladder. Many of the symptoms of gall bladder disease may mimic anorexia nervosa (AN). Laura Daly, a woman from Missouri, suffered from an inherited disorder in which the gall bladder was not properly attached; the resultant complications led to multiple erroneous diagnoses of AN. Upon performance of a CCK test, standard imaging techniques are done with the patient lying prone, in this instance it was done with the patient in an upright position. The gall bladder was shown to be in an abnormal position having flipped over the liver. The gallbladder was removed and the patient has since recovered. The treatment was performed by William P. Smedley, M.D., F.A.C.S.in Pennsylvania.

colonic tuberculosis misdiagnosed as anorexia nervosa in a physician at the hospital where she worked. "This patient, who had severe wasting, was misdiagnosed as having anorexia nervosa despite the presence of other symptoms suggestive of an organic disease, namely, fever and diarrhea"(Madani, A 2002).[60]

Crohn's Disease: "We report three cases of young 18 to 25 year-old girls, initially treated for anorexia nervosa in a psychiatric department. Diagnosis of Crohn's disease was made within 5 to 13 years."(Blanchet C, Luton JP. 2002)"This disease should be diagnostically excluded before accepting anorexia nervosa as final diagnosis". (Wellmann W et al.)[61][62][63][64]

Insulinomas, are (pancreatic tumors) that cause an overproduction of insulin causing hypoglycemia. Various neurological deficits have been ascribed to this condition including misdiagnosis as an eating disorder.[65][66][67][68][69]

cestodes (tapeworm) infestations can affect various regions of the human body including the gastrointestinal and neuroendocrine systems. While most of those infected are asymptomatic, infestations can cause psychiatric symptoms, epilepsy, megoblastic anemia, weight gain or loss.

Cysticercosis is an infection caused by the larval stage of the pork tapeworm (Taenia solium). The larval stage of T. solium can create cysts in various regions of the body including the brain (neurocysticercosis). Hypothalimic cysticercosis has been associated with obesity. Cysts may form in the bile and pancreatic ducts causing full or partial obstruction some of the symptoms may include weight loss, anorexia, or increased appetite.[79][80]

There are multiple medical conditions which may misdiagnosed as a primary psychiatric disorder. These may have have a synergistic effect on conditions which mimic an eating disorder or on a properly diagnosed ED. They also may make it more difficult to diagnose and treat an ED.

Toxoplasmaseropositivity even in the absence of symptomatic toxoplasmosis has been linked to changes in human behavior and psychiatric disorders including those comorbid with eating disorders such as depression. In reported case studies the response to antidepressant treatment improved only after adequate treatment for toxoplasma.[82]

neurosyphilis;It is estimated that their may be up to one million cases of untreated syphyilis in the U.S. alone. "the disease can present with psychiatric symptoms alone, psychiatric symptoms that can mimic any other psychiatric illness". Many of the manifestations may appear atypical. Up to 1.3% of short term psychiatric admissions may be attributable to neurosyphilis, with a much higher rate in the general psychiatric population. Neurosyphilis like Lyme Disease has been given the appellation the "great imitator" for it may present in various ways such as depression and chronic alcoholism. (Ritchie, M Perdigao J,)[83]

dysautonomia a term used to describe a wide variety of autonomic nervous system (ANS) disorders may cause a wide variety of psychiatric symptoms including anxiety, panic attacks and depression. Dysautonomia usually involves failure of sympathetic or parasympathetic components of the ANS system but may also include excessive ANS activity. Dysautonomia can occur in conditions such as diabetes and alcoholism.

There are separate psychological disorders which may be misdiagnosed as an eating disorder.

Emetophobia is an anxiety disorder characterized by an intense fear of vomiting. A person so afflicted may develop rigorous standards of food hygiene, such as not touching food with their hands. They may become socially withdrawn to avoid situations which in their perception may make them vomit. Many who suffer from emetophobia are diagnosed with anorexia or self-starvation. In severe cases of emetophobia they may drastically reduce their food intake.[84][85]

phagophobia is an anxiety disorder characterized by a fear of eating, it is usually initiated by an adverse experience while eating such as choking or vomiting. persons with this disorder may present with complaints of pain while swallowing.[86]

Body dysmorphic disorder (BDD) is listed as a somatoform disorder that affects up to 2% of the population. BDD is characterized by excessive rumination over an actual or perceived physical flaw. BDD has been diagnosed equally among men and women. While BDD has been misdiagnosed as anorexia nervosa, it also occurs comorbidly in 39% of eating disorder cases. BDD is a chronic and debilitating condition which may lead to social isolation, major depression and suicidal ideation and attempts. Neuroimaging studies to measure response to facial recognition have shown activity predominately in the left hemisphere in the left lateral prefrontal cortex, lateral temporal lobe and left parietal lobe showing hemispheric imbalance in information processing. There is a reported case of the development of BDD in a 21 year old male following an inflammatory brain process. Neuroimaging showed the presence of new atrophy in the frontotemporal region.[87][88][89][90][91]