help w/ nursing dx/formulating my thoughts

This is driving me crazy! Maybe I'm thinking too hard about this but I'm struggling with coming up with appropriate nursing diagnoses. For my med-surg class, we have to write a fluid and electrolyte paper. We have to have four diagnoses total - two addressing an electrolyte problem and two addressing a fluid problem. There is a catch: we're not allowed to use hyper/hypo-electrolyte for the electrolyte problem and we're not allowed to use hyper/hypovolemia or risk for hyper/hypovolemia. It has to be a problem that we are concerned about related to the hyper/hypovolemia. Here is some background information on my patient:

N.S., 66 y.o. female

admitting dx: UTI, hypoglycemia

comorbidities: HTN, DM, CAD, depression, anxiety, COPD, anemia, GERD, hyperlipidemia

heplocked

I/O that day: 1840 in, 1800 out

Labs:

K+ 3.0mEq/L

Cl- 90mEq/L

CO2 37mEq/L

BUN 45mg/dL

creatinine 1.87mg/dL

RBC 3.75mil/cmm

Hgb 11.8g/dL

Hct 34.9%

even though her BUN is elevated, that can't mean dehydration because her RBCs & H/H are all low, indicating hemodilution = overload. The patient has no history of renal disease but her creatinine is elevated...so I think she has some compromised kidney function going on. She is also retaining some fluid (aeb her I/O...I know that output should be equal to the intake). For the electrolyte problem, I decided to pick hypokalemia and have the following diagnoses:

impaired physical mobility r/t muscle weakness (aeb blah blah blah...)

constipation r/t smooth muscle atony (aeb blah blah blah...)

but for the fluid problem, I'm struggling. I was thinking "risk for pulmonary edema r/t fluid volume excess" as one. As for the other, I would love to concentrate on the impaired kidney function but of course I cannot use the diagnosis, "hypervolemia r/t impaired kidney function aeb..." it has to be the other way around, but "impaired kidney function" isn't really a NANDA diagnosis. I was also thinking of "Impaired gas exchange r/t fluid volume overload secondary to COPD aeb hypoventilation and increased CO2 level" as the other one, but to be honest I'm not really sure. I already e-mailed my instructor regarding this. She helped point me in the right direction that this patient is more at risk for (or has) hypervolemia as opposed to hypovolemia, but of course it's up to me to come up with the diagnoses. Any help would be great. Thanks!