Brief Answer:
Intestinal infection with possible bleeding, to go to ER if it persists.

Detailed Answer:
Hi.
Thanks for your information (there is no query as such).

To recapitulate: Wednesday had cramps with loose stool, severe chills and mild low back pain - Late Thursday ''black'' diarrhea - took only Pepto Bismal - Eating antagonizes eaten light - known diverticulosis - Yesterday sleepy and had sound sleep - in a Female patient of 67 years.

To correlate:
Cramps, chills, loose stools, mild low back pain - all suggest there is an intestinal infection
Black diarrhea - called as malena suggests that there is a bleeding in some part of the intesines.
Malena could have been anywhere from the GI (Gastrointestinal) tract, most probably from the gastritis or gastric ulcer as per your history or from the diverticulosis is converted to diverticulitis (infection).

I would advise in such a patient the following:
-Consultation with a Gastroenterologist for clinical examination, Upper GI Endoscopy, Colonoscopy and other investigations like:
Blood: CBC for infection ,Hemoglobin since there is bleeding, liver and kidney
functions , blood sugar and blood group, elctrolytes
Urine : routine and microscopy.
Stool: Routine, microscopy, culture and sensitivity, Occult blood.
Ultrasonography and CT scan as may be suggested.
-Admission to the hospital to control infection with antibiotics, metronidazole, probiotic, maintenance of hydration, electrolytes, hemoglobin, monitoring; control of bleeding after finding the source.

In a nutshell, this looks to be a serious problem or can turn into complications considering your age and the symptoms you have noted, hence it is better to see a doctor at the earliest.

I hope this answer helps you to get a proper diagnosis, and get a proper further treatment. Please feel free to ask for more or if you need further clarifications if you feel there is a gap of communication.

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