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  #1  
Old 06-27-2011
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Question Lab studies in a bulimic patient!

A 14 year old girl is brought to the physician by her mother. The girl has lost 15 lbs in 3 months. Mother says she observed her daughter eating large amounts of food and drinks soft drinks frequently, she suspects if her daughter is bulimic. Which of the following lab studies will be elevated?

A. Serum bicarbonate
B. Serum blood urea nitrogen
C. Serum sodium
D. Serum glucose
E. Serum calcium.
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Old 06-27-2011
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A. Serum bicarbonate

If she is repeatedly purging then she will lose lots of H+ leading to metabolic alkalosis.
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Old 06-27-2011
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Correct Answer D is the right answer

Serum glucose will be elevated. This patient has type 1 DM, Hence pt eats a lot and drinks soft drinks frequently, without getting obese.

Lesson learnt is child with weight loss despite eating deserves a blood glucose study. Its important not to suspect every teenager with weight loss to have bullimia in practice n in usmle.

@ Patel MD, mother suspects pt is bullimic, but there is no evidence of the pt purging in the question.
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Old 06-27-2011
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Hmm that's odd, what part of the question stem pointed to DM?
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Old 06-27-2011
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Yeah, nothing in the question stem suggests DM, and the stem directly leads you to think what is the abnormality in bulimia. Good point with having other things on our differential, but lucky for us on the USMLE if they want you to think DM they tell you about ketonuria, polydypsia, polyuria, etc, i.e. things that you wouldn't confuse with bulimia.
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Old 06-27-2011
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yup. what is the source of this Q?i think it's not in usmle standard pattern.
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Old 06-27-2011
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Ya, even i got it wrong in my practice tests.. But 40 percent of them got it right. Its a question from standard q-banks..
I think the question does suggest polydipsia, polyphagia, no weight loss, age, all this do suggest type 1 DM.. the misleading part is mother thinks bullimia..
If the pt was bullimic, the question usually suggests purging, use of emetics, parotitis, hand calluses etc.. , which are not there.

Quote:
Originally Posted by patelMD View Post
Hmm that's odd, what part of the question stem pointed to DM?
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Old 06-27-2011
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Quote:
Originally Posted by mle2resident View Post
Ya, even i got it wrong in my practice tests.. But 40 percent of them got it right. Its a question from standard q-banks..
I think the question does suggest polydipsia, polyphagia, no weight loss? (She had weight loss), age, all this do suggest type 1 DM.. the misleading part is mother thinks bullimia..
If the pt was bullimic, the question usually suggests purging, use of emetics, parotitis, hand calluses etc.. , which are not there.
Thats weird, this question is bad! Because it also suggested Bulimia
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Old 06-27-2011
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if it is bulimia why u say bicarb should go up? vomiting cause hcl loss so having MA then bicarb goes down for compensationam i right?
in contrast if she is bullemic she would loss water so bun goes up
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Quote:
Originally Posted by dr_lizard View Post
if it is bulimia why u say bicarb should go up? vomiting cause hcl loss so having MA then bicarb goes down for compensationam i right?
in contrast if she is bullemic she would loss water so bun goes up
Yep, that's the reasoning behind it, but a metabolic acidosis is compensated by a respiratory alkalosis!
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Quote:
Originally Posted by patelMD View Post
Yep, that's the reasoning behind it, but a metabolic acidosis is compensated by a respiratory alkalosis!
it's metabolic alkalosis in first place. then do bicarb goes up for that?? why?how?
also u agree BUN will rise either!
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Old 06-27-2011
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ooops.. i did mean to say weight loss.
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Old 06-27-2011
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Yes.. thats the right explanation.. as the bicarb ll not be elevated in this case. U got it right buddy.
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Quote:
Originally Posted by dr_lizard View Post
it's metabolic alkalosis in first place. then do bicarb goes up for that?? why?how?
also u agree BUN will rise either!
No i meant that if you lose the H+, then you will have an increase in Bicarbonate, meaning Increased Serum Bicarb...

You got me all mixed up
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Quote:
Originally Posted by mle2resident View Post
Yes.. thats the right explanation.. as the bicarb ll not be elevated in this case. U got it right buddy.
That can't be the explanation, but regardless.. i'm sure the real exam will be have better questions
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Quote:
Originally Posted by mle2resident View Post
Yes.. thats the right explanation.. as the bicarb ll not be elevated in this case. U got it right buddy.
that;s why i go with rise of BUN(as i thought pt is not diabetic)!
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Quote:
Originally Posted by dr_lizard View Post
that;s why i go with rise of BUN(as i thought pt is not diabetic)!
So what's your diagnosis?

mle2resident says its DM? lol
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phew.. this question is making me go
The intention of this question is to not conclude every teenager with polyphagia to bullimia.. U have to differentiate with type 1 DM, and Hyperthyroidism.
However this question does not say any classical picture of any, but the first test to be done in a patient with these symptoms is a blood glucose check.
Thats the only message i am gonna take from this question.
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Quote:
Originally Posted by patelMD View Post
No i meant that if you lose the H+, then you will have an increase in Bicarbonate, meaning Increased Serum Bicarb...

You got me all mixed up
i think i need to read acid base chapter again as here is 12 midnight my brain is not functioning any more for acid base discussions!!!
but i hope exams Qs won't be like this.:sorry:
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Old 06-27-2011
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lol, weird question and even weirder discussion! Just to put it out there, vomiting causes you to lose HCL, resulting in increased bicarbonate and metabolic alkalosis. The compensatory response to this is to hypoventilate, thereby retain CO2 to lower the pH back to normal. Also, very little bicarb is excreted renally so it's usually not a mechanism of compensation for alkalosis.
Also, when you think of BUN you should think kidney; usually the BUN levels is dependent on whether or not the kidney can get rid of it (think azotemia). When she vomits, she is not really losing water since she drinks to replace what's loss (i.e she is not chronically dehydrated because unless she is in a desert somewhere she's drinking water). The problem is she is not replacing the acid, hence the acid/base disturbance.
But since this is a diabetes question, this is just an aside
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  #21  
Old 07-29-2012
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I found a similar question on the kaplan qbank. It reads: "A 14-year-old girl is brought to the physician by her mother because of concerns about a possible eating disorder. For the past 2 months, the patient drank nothing but diet soda and water and has had a 6.8 kg (15-lb.) weight loss. She occasionally eats two dinners, but her parents do not know if she purges. The girl denies any problems with her self-image and wishes she could keep her weight up, as she feels her weight loss is limiting her ability as an athlete. She has had increased weakness and fatigue over the past 1 month and increased frequency of urination without dysuria. She has had no major medical illnesses and takes no medications. Examination shows a thin, well appearing teenager. Which of the following is most likely to confirm the patient's condition?

A. Antiglutamic acid decarboxylase antibodies
B. Elevated fasting cholesterol and triglyceride levels
C. Parotid gland hypertrophy and loss of tooth enamel
D. Significant proteinuria on a urine dipstick
E. Retinal vessel proliferation

Correct answer A. These antibodies are associated with DM1. I hate it how they want to confuse you. What do they mean with "for the past 2 months drank nothing but diet soda and water"
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Old 07-29-2012
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What is the explanation given by Kaplan ?


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