var pipeline = new EmptyPipelineDefinition<ChangeStreamDocument<BsonDocument>>();
var options = new ChangeStreamOptions() { FullDocument = ChangeStreamFullDocumentOption.UpdateLookup };
using (var cursor = collection.Watch(pipeline, options))
{
    var numberOfChunks = 1;
    var filler = new string('x', (numberOfChunks - 1) * 65536);
    var document = new BsonDocument { { "_id", 1 }, { "filler", filler } };
    collection.InsertOne(document);

    while (true)
    {
        cursor.MoveNext();
        var change = cursor.Current.FirstOrDefault();
        if (change != null)
        {
            break;
        }
    }
}