I'm posting my recent experience with Phallus Prostration in one of my Indian Runner Drakes recently for future reference for others.
"Woody," he got his name after this experience, was about 16.5 weeks old, just coming into full maturity I believe. He along with 3 others this age, became "active" in pursuing the females. He was the most aggressive about it and one of the more overall dominant. One morning I noticed he would single off from the bunch (37 total, Runners, Khaki, Swedish) with a younger Khaki chasing him, and noticed Woody's Phallus hanging out. The Khaki thought it was a worm I suppose. It wasn't that way the evening before so I know I caught it very quick.
I secluded him and resorted to "Storey's Guide to Raising Ducks" and BYC for help. I didn't get a good photo of the Phallus at time of Prostration but I'm glad to see "decomposed" in this thread had a good photo for reference. Woody was hanging out about 4-5 inches. I cleaned him up with some diluted chlorahexidine (sp?) solution (used to sterilize and clean in vet office I used to work at, you can also get it at feed stores and some pet stores). I used an A&D type ointment to help moisturize and lube with no success at getting it to go back in.
I continued to use neosporine and ointment daily after cleaning. The following day he retracted about an inch or so. After that no further retraction occurred. It started to get red over a few days, not infected, just inflamed from dragging around and I caught him billing at it several times. After several days the skin on the surface became dry and sloughed off for several more days. After about a week and a half the phallus hanging out began to deteriorate and turn gray. After two weeks I decided not to continue with ointment, expecting it dry and fall off. Almost two and half weeks later of it not changing, I thought I would take a look at him the following day and be ready to cut it off. I was sure it was dead and I was prepared for bleeding and suturing if necessary.
However, the following day I didn't notice it was hanging down. I took him out to look, thinking it was stuck to his feathers or something (hoping it had fallen off). It had fallen off and I found it in his water bin. I was somewhat surprised to find that the part that turned black to fall off was internal, suspecting just inside his vent. I was thinking it wouldn't fall off because the part hanging out was just gray and not turning black. But the tissue must have not turned black because of the ointments and water keeping it more supple, is my guess.
I did take a photo of the discarded phallus to show what it looks like afterwards. It took 2.5 weeks approximately to fall off. I suspect it was dying, and was dead enough he could have pulled it off himself. He was constantly shaking his tail end and periodically fussing with it. Other than being distraught for not being with the flock, he did fine and otherwise was healthy. At first I had him in med pen away from flock, but after a couple days I built a med pen next to the flock pen. He started to eat better being closer, and his friends were right on the other side of the fence visiting with him. The day I inspected him and found his phallus had fallen off, I put him in the drake only pen.
On a side note, I noticed he was being dominated by a Khaki drake that was previously dominated by him. So I am suspecting his absence from the flock changed the pecking order. Which also switched up a little after separating out at least half the drakes in my whole flock. I'm nearly at 50/50. I hope this is helpful to someone who is considering options in care for their ducks.
This is the Prostrated Phallus that was sloughed off after 2.5 weeks. It is approximately 4 inches. The black portion at the right, was internal. The majority of the grey length was what was hanging out.