Last week, Alex presented an interesting case of fever and we went through the work-up and approach. The patient was an elderly woman who presented with fevers at home. No source of fever was initially found and there were no localizing symptoms on history or exam.
We see fever so often, whether it be on admission or during the patient’s stay. It is important to think through the causes of fever and do our due diligence in the work-up. Fever of unknown origin is something you will commonly encounter in your practice.
Definition: Fever of Unknown Origin
- Temp >101
- >3 days inpatient, or >3 outpatient visits
- Immunocompetent
The above is the most modern version of the definition to reflect current day practices. Previous definition said you needed fever for >3 weeks and failure to reach diagnosis after >1 week of inpatient work-up.
Mnemonic for Fever:
A – Autoimmune
T – Thrombosis
A – Arteritis
D – Drugs
T – Thyrotoxicosis
E – Environment
M – Malignancy
P – Pheo/Psych Meds
N – Neuroleptic Malignant Syndrome
M – Malignant Hyperthermia
S – Serotonin Syndrome
Hidden Causes of Fever:
A – Abscess
E – Endocarditis
I – Indwelling plastic/hardware
O – Osteo
U – UTI
Remembering your approach when you head to the ER and begin working up the patient will help level up your questions during the interview and what you will look for during your physical exam.
Paragraph 2 questions to ask:
-IV drug use (viral hepatitis, endocarditis), known exposures to TB, homelessness, weight-loss (TB), travel, trauma (hematoma, abscess), sexual encounters (Syphilis, acute onset HIV)
-Joint swelling or pain, rashes, muscle weakness, family history of rheumatologist disease; bloody diarrhea, abdominal pain (IBD); headache, vision changes (GCA)
-Weight loss (malignancy), bruising, bleeding, fatigue (leukemia, lymphoma, MDs); cough (metastatic cancer to lungs); volume overload (atrial myxoma (volume overload in combination with fever, weight loss arthralgia, extra heart sound); hematuria (RCC)
-Recent travel, leg swelling (DVT); alcohol use (alcoholic hepatitis); tremor, diaphoresis, weight loss (hyperthyroidism)
Second Tier Physical Exam:
-Point tenderness looking for epidural abscess, head-to-toe skin exam, look for ulcers in bed bound patient, look in pharynx, tract marks and evidence of skin popping, rectal exam, look for Osler nodes and janeway lesions.
-Joint exam, assess for petechiae (especially dependent areas), strength exam
-Splenomegaly, palpation of liver edges
-Thyroid exam, unilateral leg swelling
Labs in fever of unknown origin:
-Cultures (Urine, Blood)
-CBC, CMP
-Peripheral Smear
-Tox screen
-ESR
-CRP – Use this to trend, especially in autoimmune disease or when you are following treatment of osteo (quicker rise and fall)
-ANA
-Lactic acid
-Ferritin – in Adult Onset Still’s Disease this is >2000
-LDH – Elevated in lymphoma
-ANCA studies
-HIV, viral hepatitis panel, Tspot, RPR
-Consider d-dimer if pretest probability for PE/DVT is low
-TSH
What imaging do you start with?
Abdominal U/S or abdominal CT
This patient was incidentally found to have aortitis seen on a CT of the abdomen done prior to the admission. At the point of our discussion the Aorititis seen on imaging was a concerning cause for her fevers and further work-up with an angiogram as well as rheumatologic and infectious labs were being done.. Now let’s review a quick approach to aortitis that comes from Clinical Problem Solvers. Aortitis is a rare disorder and actually has many causes. The following approach helps keep our differential board and helps direct our work-up.
References:
“Dx Schema – Aortitis.” The Clinical Problem Solvers, 31 Dec. 2019, clinicalproblemsolving.com/dx-schema-aortitis/.
Mansoor, André M. Frameworks for Internal Medicine. Wolters Kluwer, 2019.
Lopes RJ, Almeida J, Dias PJ, Pinho P, Maciel MJ. Infectious thoracic aortitis: a literature review. Clin Cardiol. 2009;32(9):488-490. doi:10.1002/clc.20578