Are rhubarb leaves toxic?

I had always been told that rhubarb leaves are extremely toxic, but my research has confused me. Some sources say that it is hardly toxic, while others say it is lethal. Do you know how toxic rhubarb leaves actually are?

Rhubarb leaves are toxic and humans should never ingest them. The stems are safe to eat.

Symptoms caused by rhubarb leaf ingestion

According to the U.S. National Library of Medicine at the National Institutes of Health symptoms can include:

Breathing difficulty
Burning in the mouth
Burning in the throat
Coma
Diarrhea
Eye pain
Kidney stones
Nausea
Red-colored urine
Seizures
Stomach pain
Vomiting
Weakness

Serious poisonings can result in kidney failure. Deaths have been reported, but are rare.

Severity of symptoms

The severity of symptoms caused by consuming rhubarb is determined by:

Patient's age, weight, and condition
The variety of rhubarb
How long it was swallowed before treatment
Amount swallowed.